January 2016 - Pharo-users - lists.pharo.org

Re: [Pharo-users] I am David Allouche, let me introduce myself.

by Dimitris Chloupis

"I have seen someone in another thread expressing the desire for namespaces. As a newcomer, I also feel that is something important and missing. But since one of the goals of Pharo is to produce an environment that can be understood by a single person, the lack of namespace might actually be a feature. Namespace are essential for languages like C++, designed for large projects, produced by large teams, where nobody understands the whole system. They embody an industrial approach to programming. In contrast, I have the impression that Smalltalk emphasises regularity to minimise system size, rather than modularity to manage system size, and that it embodies a craftsmanship approach." Pharo contains over 800000 methods spread around several thousands classes and the system has not imploded yet even though we have no namespaces. The reasoning is simple, Pharo does not need namespaces because its not a programming language. Namespaces primary role is not organization so much as prevention of name clashes , this is not a problem for Pharo since it does not allow name clashes in the first place. Thats is happening in the enviroment and not language level, if you want to organise your classes you use packages . Packages also are not part of the language and are also implemented on enviroment level, though one could argue that language is also part of the enviroment. So yes it feelt strange even for not having namespace coming from python but after coding in pharo for over a year its clear to me that pharo does not need it and would probably benefit by more sophisticated and specific implementation when it comes to organisations. But generally speaking we already have plenty of tools that help you locate classes and methods with ease, so that is not much of a problem. Pharo enviroment is far from simple, quite the contrary Smalltalk implementations were always far more complex than you average language like C++, the big diffirence is that the enviroment is constructed in such way to help you deal with complexity. Where modern languages ephasize simplicity pharo and smalltalk in general invest on better dealing with complexity , hence why Smalltalk has been very popular in specific very complex fields like Banking Sector, Shipping etc. C++ is no where as suitable for complex applications , its popularity merely stems from the fact that is OS language with immediate access to OS libraries and massive support. On Wed, Jan 13, 2016 at 7:30 PM David Allouche <david(a)allouche.net> wrote: > Thank you everyone for the kind responses. I will answer some of the > questions and suggestions here. > > To get faster to the intellectual stimulation, pick a task / project and > start asking questions. And have fun :). > > > That is good advice, but right now I think I will just explore the system, > review changes, and wait for the tasks to find me. There are already more > things I want to do than I will probably every be able to accomplish :-) > > I think when people referring to Smalltalk refer to Smalltalk as the > language or OOP itself, but thats only the tip of the iceberg, Pharo tries > to stay true to vision of smalltalk creating the virtual enviroment where > the user can easily create his or her own tools or modifying the existing > ones, something that I feel no other language out there can emulate because > they follow a non monolithic approach where there is a deep dichotomy > between language, libraries and the environment itself. You could say that > Smalltalk is the anti-Unix architecture , a great example of monolithic > design that works great in practice yet its easy to modify and extend. > > > The fact Smalltalk the language cannot be taken in isolation from > Smalltalk the environment became clear rather early on: reading the UPBE > and other materials shows that the language itself does almost nothing: it > cannot even define classes or packages. It is all part of the environment. > > I have seen someone in another thread expressing the desire for > namespaces. As a newcomer, I also feel that is something important and > missing. But since one of the goals of Pharo is to produce an environment > that can be understood by a single person, the lack of namespace might > actually be a feature. Namespace are essential for languages like C++, > designed for large projects, produced by large teams, where nobody > understands the whole system. They embody an industrial approach to > programming. In contrast, I have the impression that Smalltalk emphasises > regularity to minimise system size, rather than modularity to manage system > size, and that it embodies a craftsmanship approach. > > Since I am just old enough to remember a time where computer systems could > be understood by a single person, I find it an attractive idea to try and > produce a modern system with that property. > > I can't remember who famous said something like "The only languages > worth learning are the ones that changes the way you think about > programming..." and I found that with Smalltalk & Pharo. > > > I am familiar with that idea too. And most good languages provide that. > > One day I will have learn some language from the ML family. I choose > Smalltalk because it clearly had such a strong influence on the thinking of > people who have used it, I thought I could learn > > A good way to get your hands dirty is to review fixes submitted by > others... > https://pharo.fogbugz.com/default.asp?pgx=LF&ixFilter=45 > There are never enough hands there :) (my own action here fluctuates > from time to time) > > > I will try to spend some time reviewing code. That is a good way to get > exposed to things one does not even know they exist. > > Did you look at Seaside? > Since you should be able to read french there is a nice tutorial: > tinyBlog. In two days you can build a small web app > with a mongo back end. > > > I have no looked at Seaside yet, I have not even read the corresponding > chapter in UPBE. But I certainly will, eventually. The web is an essential > part of society today. > > Where are you located ? > > > Paris, France. > > It did occur to me that the Pharo community does have a unusually large > fraction of french people. But that is not a factor for me. > > Thanks again for all the kind words. I am sure this journey is going to be > a lot of fun. :-) > > >

Jan. 13, 2016

Re: [Pharo-users] Failling Tests are green if BlockCannotReturn exception

by Sven Van Caekenberghe

> On 13 Jan 2016, at 18:42, abdelghani ALIDRA <alidrandco(a)yahoo.fr> wrote: > > Thank you all for your responses. > > I see your point about returning from a block. Because the return in this example is very explicit. But what if I put (by mistake) a return in a block in a method that is called by the test method (or even in a method that is called by another method that is called by the test method) then I would have no reason to doubt my test was successful whereas it would have failed if it was run till the last assertion. > > My point is, would it not be interesting to report tests that were not run successfully till the end? An empty test is successful. A test only fails when an assertion fails. Assertions must be written explicitly. Your suggestion is not per se a bad idea, it is just not within the contract of SUnit, I think. > Abdelghani > > > De : Sven Van Caekenberghe <sven(a)stfx.eu> > Ã : abdelghani ALIDRA <alidrandco(a)yahoo.fr>; Any question about pharo is welcome <pharo-users(a)lists.pharo.org> > EnvoyÃ© le : Mardi 12 janvier 2016 7h35 > Objet : Re: [Pharo-users] Failling Tests are green if BlockCannotReturn exception > > > > > > On 12 Jan 2016, at 00:26, abdelghani ALIDRA <alidrandco(a)yahoo.fr> wrote: > > > > Hi, > > > > I observed this unexpected behavior in test classes. > > In a test class define a method : > > > > testBlock > > |aBlock| > > aBlock := [ ^1 ]. > > aBlock value. > > self assert: false. > > > > Althought the assertion is false at the end of the test, the test is green. > > Actually, It does not matter what you put after aBlock value, the test always succedes (I tried to put a self halt, it does not execute) > > The test is 'does an explicit return from a block return from the whole method'. Of course it does. But if it would not, you would arrive at the self assert: false and the test would fail. You see ? > > BTW, this can also be written as self fail - search for the senders of that message for more examples. > > > > I tried this both in Pharo 4 and 5 under Windows and MacOS. > > > > Any ideas? > > > > Cheers > > Abdelghani > > > > > >

Jan. 13, 2016

Re: [Pharo-users] Understanding the role of the sources file

by David Allouche

> On 13 Jan 2016, at 18:14, Dimitris Chloupis <kilon.alios(a)gmail.com> wrote: > > Why the Cog VM is mentioned in my documentation is no accident. There is another VM that is called Stackless VM or old VM that was the VM before Cog that had no JIT and its a VM we still use for platforms that Cog VM does not currently run like Raspberry Pi, Android and I think iOS too. > > > "But nowadays, JIT compiling byte-code to machine language are the norm rather than the exception, so I do not think it is worth mentioning." > > Definitely not the norm Python and Ruby VMs are not JIT, generally speaking JIT compilers are rare for Dynamic languages like Pharo. Python has PyPy which is a JIT VM but is nowhere as popular as Cpython. You are right. The JIT is worth mentioning there. > > CPython people try to avoid JIT because it makes VM architecture much more complex. At least thats their argument. I am getting off-topic, but since I have already written what follows, and I think it is informative, I am leaving it there :-) Python is a rather large language, with a large number of quirks that need to be preserved to provide full compatibility. It is also a language with advanced introspection, and very dynamic semantics, even more than Smalltalk in some aspects. And its main implementation (CPython) has very highly optimised data structures and memory management. That makes it really difficult to implement correctly and and to improve performance without slowing down other parts. Before PyPy, Google funded the Unladen Swallow project, that tried to produce a Python JIT using LLVM, this project was abandoned. Even PyPy needs to make frequent and expensive guard tests to ensure that invariants required for JIT are preserved. It does bring a significant speed boost (2x-10x), but at the expense of slow startup and increased memory footprint (~2x). However, it seems clear that the long term future of Python lies in PyPy. In particular, they have high hopes to solve the lack of multicore support by implementing software transactional memory in the medium term, until hardware transactional memory is advanced enough to be usable there. > Another big advantage of Pharo is that it has luxury to come with a JIT included and well tested. I guess the simplicity of the language makes it relatively easy to produce a JIT. This is indeed a very good thing. > > The only popular JITs out there are Java's and .NET, dont know if Javascript V8 use JIT as well, but thats pretty much it. But bytecode is very popular indeed. V8 does use JIT. I believe it was the first widely deployed language implementation to use a tracing interpreter to JIT a language with latent typing. I believe all the other major Javascript implementations have followed suite. This is also the approach used by PyPy. Java and .Net have static typing, so they do not require a tracing interpreter to compile to machine code. > On Wed, Jan 13, 2016 at 6:43 PM David Allouche <david(a)allouche.net <mailto:david@allouche.net>> wrote: >> On 13 Jan 2016, at 16:27, Dimitris Chloupis <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: >> >> "The virtual machine (VM) provides the environment where the Pharo system lives. It is different for each operating system and hardware architecture, and runs as a machine language executable in the operating system. It implements the details of managing memory, executing Pharo byte-code, and communicating with the world outside of the Pharo system: files, other operating system process, and the network." >> >> No the environment is the image, the VM is basically what its names says, a machine emulated by software. The vast majority of tools, even the language itself reside on the image. VM is there in order for the code to be able to execute and to interface with the underlying Operating System. You could completely modify the VM , for example move it to the JVM and still the pharo enviroment would be intact. > > That is indeed the idea I tried to convey by "where the Pharo system lives", but I see how that can be misunderstood. However, I try to avoid using "big words" like "abstraction". > > How about this? > > "The virtual machine (VM) provides the portable environment to execute Pharo images. Its implementation needs to be different for each operating system and hardware architecture, as it runs as a machine language executable in the operating system. It implements the details of managing memory, executing Pharo byte-code, and communicating with the world outside of the Pharo system: files, other operating system process, and the network. > > >> "Hi Dimitris, >> your formulation "...Pharo bytcode...and convert it to machine code..." >> is insofar irritating to me as "convert it to machine code" would >> suggest to me that a compiler is at work here. Davids "executing Pharo >> byte-code" seems more understandable to me here." >> >> Thats correct its a compiler, a byte compiler, it compiles bytecode to machine code and it does it while the code executes, this is why its called JIT , which has the meaning of Just In Time compilation, meaning that machine code is compiled just before the code is executed so several optimizations can be applied that would not be known before the execution of the code. Similar to JAVA's JIT compiler. >> >> Note here that a compiler is not just something that produces machine code, a compiler for example can take one language and compile it to another language. > > That's technically true. But most readers will probably unconsciously assume that a compiler is something that produces machine language. The document should be careful to avoid misunderstandings caused by such common assumptions. > > As for the JIT, that is totally an implementation detail, and I believe it is only worth mentioning if you want to prevent the reader from assuming that Pharo is slow because its VM executes byte-code. But nowadays, JIT compiling byte-code to machine language are the norm rather than the exception, so I do not think it is worth mentioning. > > >> >> On Wed, Jan 13, 2016 at 4:58 PM Werner Kassens <wkassens(a)libello.com <mailto:wkassens@libello.com>> wrote: >> Hi Dimitris, >> your formulation "...Pharo bytcode...and convert it to machine code..." >> is insofar irritating to me as "convert it to machine code" would >> suggest to me that a compiler is at work here. Davids "executing Pharo >> byte-code" seems more understandable to me here. >> werner >> >> On 01/13/2016 02:22 PM, Dimitris Chloupis wrote: >> > I assume you have never read a an introduction to C++ then :D >> > >> > here is the final addition for the vm >> > >> > (Vm) is the only component that is different for each operating system. >> > The main purpose of the VM is to take Pharo bytcode that is generated >> > each time user accepts a piece of code and convert it to machine code in >> > order to be executed, but also to generally handle low level >> > functionality like interpreting code, handling OS events (mouse and >> > keyboard), calling C libraries etc. Pharo 4 comes with the Cog VM a very >> > fast JIT VM. >> > >> > I think its clear, precise and does not leave much room for confusion. >> > Personally I think its very important for the absolute begineer to have >> > strong foundations of understanding the fundamental of Pharo and not for >> > things to appear magical and "dont touch this". >> > >> > On Wed, Jan 13, 2016 at 2:54 PM Sven Van Caekenberghe <sven(a)stfx.eu <mailto:sven@stfx.eu> >> > <mailto:sven@stfx.eu <mailto:sven@stfx.eu>>> wrote: >> > >> > >> > > On 13 Jan 2016, at 13:42, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com> <mailto:kilon.alios@gmail.com <mailto:kilon.alios@gmail.com>>> wrote: >> > > >> > > I mentioned bytecode because I dont want the user to see at some >> > point bytecode and say "What the hell is that" I want the reader to >> > feel confident that at least understands the basic in Pharo. Also >> > very brief explanations about bytecode I have seen in similar python >> > tutorials. Obviously I dont want to go any deeper than that because >> > the user wont have to worry about the technical details on a daily >> > basis anyway. >> > > >> > > I agree that I could add a bit more on the VM description similar >> > to what you posted. I am curious though, wont even the interpreter >> > generate machine code in order to execute the code or does it use >> > existing machine code inside the VM binary ? >> > >> > No, a classic interpreter does not 'generate' machine code, it is >> > just a program that reads and executes bytes codes in a loop, the >> > interpreter 'is' machine code. >> > >> > No offence, but you see why I think it is important to not try to >> > use or explain too much complex concepts in the 1st chapter. >> > >> > Learning to program is hard. It should first be done abstractly. >> > Think about Scratch. The whole idea of Smalltalk is to create a >> > world of interacting objects. (Even byte code is not a necessary >> > concept at all, for example, in Pharo, you can compile (translate) >> > to AST and execute that, I believe. There are Smalltalk >> > implementations that compile directly to C or JavaScript). Hell, >> > even 'compile' is not necessary, just 'accept'. See ? >> > >> > > On Wed, Jan 13, 2016 at 2:25 PM Sven Van Caekenberghe >> > <sven(a)stfx.eu <mailto:sven@stfx.eu> <mailto:sven@stfx.eu <mailto:sven@stfx.eu>>> wrote: >> > > Sounds about right. >> > > >> > > Now, I would swap 1 and 4, as the image is the most important >> > abstraction. >> > > >> > > There is also a bit too much emphasis on (byte|source)code. This >> > is already pretty technical (it assume you know what compilation is >> > and so on). But I understand it must be explained here, and you did >> > it well. >> > > >> > > However, I would start by saying that the image is a snapshot of >> > the object world in memory that is effectively a live Pharo system. >> > It contains everything that is available and that exists in Pharo. >> > This includes any objects that you created yourself, windows, >> > browsers, open debuggers, executing processes, all meta objects as >> > well as all representations of code. >> > > >> > > <sidenote> >> > > The fact that there is a sources and changes file is an >> > implementation artefact, not something fundamental. There are ideas >> > to change this in the future (but you do not have to mention that). >> > > </sidenote> >> > > >> > > Also, the VM not only executes code, it maintains the object >> > world, which includes the ability to load and save it from and to an >> > image. It creates a portable (cross platform) abstraction that >> > isolates the image from the particular details of the underlying >> > hardware and OS. In that role it implements the interface with the >> > outside world. I would mention that second part before mentioning >> > the code execution. >> > > >> > > The sentence "The purpose of the VM is to take Pharo bytcode that >> > is generated each time user accepts a piece of code and convert it >> > to machine code in order to be executed." is not 100% correct. It is >> > possible to execute the byte code without converting it. This is >> > called interpretation. JIT is a faster technique that includes >> > converting (some often used) byte code to machine code and caching that. >> > > >> > > I hope this helps (it is hard to write a 'definitive explanation' >> > as there are some many aspects to this and it depends on the >> > context/audience). >> > > >> > > > On 13 Jan 2016, at 12:58, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com> <mailto:kilon.alios@gmail.com <mailto:kilon.alios@gmail.com>>> wrote: >> > > > >> > > > So I am correct that the image does not store the source code, >> > and that the source code is stored in sources and changes. The only >> > diffirence is that the objects have a source variable that points to >> > the right place for finding the source code. >> > > > >> > > > This is the final text if you find anything incorrect please >> > correct me >> > > > >> > > > --------------- >> > > > >> > > > 1. The virtual machine (VM) is the only component that is >> > different for each operating system. The purpose of the VM is to >> > take Pharo bytcode that is generated each time user accepts a piece >> > of code and convert it to machine code in order to be executed. >> > Pharo 4 comes with the Cog VM a very fast JIT VM. The VM executable >> > is named: >> > > > >> > > > â¢ Pharo.exe for Windows; â¢ pharo for Linux ; and >> > > > >> > > > â¢ Pharo for OSX (inside a package also named Pharo.app). >> > > > The other components below are portable across operating >> > systems, and >> > > > >> > > > can be copied and run on any appropriate virtual machine. >> > > > >> > > > 2. The sources file contains source code for parts of Pharo >> > that donât change frequently. Sources file is important because the >> > image file format stores only the bytecode of live objects and not >> > their source code. Typically a new sources file is generated once >> > per major release of Pharo. For Pharo 4.0, this file is named >> > PharoV40.sources. >> > > > >> > > > 3. The changes file logs of all source code modifications since >> > the .sources file was generated. This facilitates a per method >> > history for diffs or re- verting.That means that even if you dont >> > manage to save the image file on a crash or you just forgot you can >> > recover your changes from this file. Each release provides a near >> > empty file named for the release, for example Pharo4.0.changes. >> > > > >> > > > 4. The image file provides a frozen in time snapshot of a >> > running Pharo system. This is the file where the Pharo bytecode is >> > stored and as such its a cross platform format. This is the heart of >> > Pharo, containing the live state of all objects in the system >> > (including classes and methods, since they are objects too). The >> > file is named for the release (like Pharo4.0.image). >> > > > >> > > > The .image and .changes files provided by a Pharo release are >> > the starting point for a live environment that you adapt to your >> > needs. Essentially the image file containes the compiler of the >> > language (not the VM) , the language parser, the IDE tools, many >> > libraries and acts a bit like a virtual Operation System that runs >> > on top of a Virtual Machine (VM), similarly to ISO files. >> > > > >> > > > As you work in Pharo, these files are modified, so you need to >> > make sure that they are writable. The .image and .changes files are >> > intimately linked and should always be kept together, with matching >> > base filenames. Never edit them directly with a text editor, as >> > .images holds your live object runtime memory, which indexes into >> > the .changes files for the source. It is a good idea to keep a >> > backup copy of the downloaded .image and .changes files so you can >> > always start from a fresh image and reload your code. However the >> > most efficient way for backing up code is to use a version control >> > system that will provide an easier and powerful way to back up and >> > track your changes. >> > > > >> > > > The four main component files above can be placed in the same >> > directory, although itâs also possible to put the Virtual Machine >> > and sources file in a separate directory where everyone has >> > read-only access to them. >> > > > >> > > > If more than one image file is present in the same directory >> > pharo will prompt you to choose an image file you want to load. >> > > > >> > > > Do whatever works best for your style of working and your >> > operating system. >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > On Wed, Jan 13, 2016 at 12:13 PM Sven Van Caekenberghe >> > <sven(a)stfx.eu <mailto:sven@stfx.eu> <mailto:sven@stfx.eu <mailto:sven@stfx.eu>>> wrote: >> > > > >> > > > > On 13 Jan 2016, at 10:57, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com> <mailto:kilon.alios@gmail.com <mailto:kilon.alios@gmail.com>>> wrote: >> > > > > >> > > > > I was adding a short description to the UPBE about sources >> > file , I always thought that the sources file is the file that >> > contains the source code of the image because the image file itself >> > stores only the bytecode. >> > > > > >> > > > > However its just came to my attention that the sources file >> > does not contain code that is recently installed in the image. >> > > > > >> > > > > So how exactly the sources file works and what it is ? >> > > > >> > > > The main perspective is from the object point of view: methods >> > are just objects like everything else. In order to be executable >> > they know their byte codes (which might be JIT compiled on >> > execution, but that is an implementation detail) and they know their >> > source code. >> > > > >> > > > Today we would probably just store the source code strings in >> > the image (maybe compressed) as memory is pretty cheap. But way back >> > when Smalltalk started, that was not the case. So they decided to >> > map the source code out to files. >> > > > >> > > > So method source code is a magic string (RemoteString) that >> > points to some position in a file. There are 2 files in use: the >> > sources file and the changes file. >> > > > >> > > > The sources file is a kind of snapshot of the source code of >> > all methods at the point of release of a major new version. That is >> > why there is a Vxy in their name. The source file never changes once >> > created or renewed (a process called generating the sources, see >> > PharoSourcesCondenser). >> > > > >> > > > While developing and creating new versions of methods, the new >> > source code is appended to another file called the changes file, >> > much like a transaction log. This is also a safety mechanism to >> > recover 'lost' changes. >> > > > >> > > > The changes file can contain multiple versions of a method. >> > This can be reduced in size using a process called condensing the >> > changes, see PharoChangesCondenser. >> > > > >> > > > On a new release, the changes file will be (almost) empty. >> > > > >> > > > HTH, >> > > > >> > > > Sven >> > > > >> > > > >> > > > >> > > >> > > >> > >> > >>

Jan. 13, 2016

Re: [Pharo-users] Failling Tests are green if BlockCannotReturn exception

by abdelghani ALIDRA

Thank you all for your responses. I see your point about returning from a block. Because the return in this example is very explicit. But what if I put (by mistake) a return in a block in a method that is called by the test method (or even in a method that is called by another method that is called by the test method) then I would have no reason to doubt my test was successful whereas it would have failed if it was run till the last assertion. My point is, would it not be interesting to report tests that were not run successfully till the end? Abdelghani DeÂ : Sven Van Caekenberghe <sven(a)stfx.eu> ÃÂ : abdelghani ALIDRA <alidrandco(a)yahoo.fr>; Any question about pharo is welcome <pharo-users(a)lists.pharo.org> EnvoyÃ© le : Mardi 12 janvier 2016 7h35 ObjetÂ : Re: [Pharo-users] Failling Tests are green if BlockCannotReturn exception > On 12 Jan 2016, at 00:26, abdelghani ALIDRA <alidrandco(a)yahoo.fr> wrote: > > Hi, > > I observed this unexpected behavior in test classes. > In a test class define a method : > > testBlock >Â Â |aBlock| >Â Â aBlock := [ ^1 ]. >Â Â aBlock value. >Â Â self assert: false. > > Althought the assertion is false at the end of the test, the test is green. > Actually, It does not matter what you put after aBlock value, the test always succedes (I tried to put a self halt, it does not execute) The test is 'does an explicit return from a block return from the whole method'. Of course it does. But if it would not, you would arrive at the self assert: false and the test would fail. You see ? BTW, this can also be written as self fail - search for the senders of that message for more examples. > I tried this both in Pharo 4 and 5 under Windows and MacOS. > > Any ideas? > > Cheers > Abdelghani > >

Jan. 13, 2016

Re: [Pharo-users] I am David Allouche, let me introduce myself.

by David Allouche

Thank you everyone for the kind responses. I will answer some of the questions and suggestions here. > To get faster to the intellectual stimulation, pick a task / project and start asking questions. And have fun :). That is good advice, but right now I think I will just explore the system, review changes, and wait for the tasks to find me. There are already more things I want to do than I will probably every be able to accomplish :-) > I think when people referring to Smalltalk refer to Smalltalk as the language or OOP itself, but thats only the tip of the iceberg, Pharo tries to stay true to vision of smalltalk creating the virtual enviroment where the user can easily create his or her own tools or modifying the existing ones, something that I feel no other language out there can emulate because they follow a non monolithic approach where there is a deep dichotomy between language, libraries and the environment itself. You could say that Smalltalk is the anti-Unix architecture , a great example of monolithic design that works great in practice yet its easy to modify and extend. The fact Smalltalk the language cannot be taken in isolation from Smalltalk the environment became clear rather early on: reading the UPBE and other materials shows that the language itself does almost nothing: it cannot even define classes or packages. It is all part of the environment. I have seen someone in another thread expressing the desire for namespaces. As a newcomer, I also feel that is something important and missing. But since one of the goals of Pharo is to produce an environment that can be understood by a single person, the lack of namespace might actually be a feature. Namespace are essential for languages like C++, designed for large projects, produced by large teams, where nobody understands the whole system. They embody an industrial approach to programming. In contrast, I have the impression that Smalltalk emphasises regularity to minimise system size, rather than modularity to manage system size, and that it embodies a craftsmanship approach. Since I am just old enough to remember a time where computer systems could be understood by a single person, I find it an attractive idea to try and produce a modern system with that property. > I can't remember who famous said something like "The only languages > worth learning are the ones that changes the way you think about > programming..." and I found that with Smalltalk & Pharo. I am familiar with that idea too. And most good languages provide that. One day I will have learn some language from the ML family. I choose Smalltalk because it clearly had such a strong influence on the thinking of people who have used it, I thought I could learn > A good way to get your hands dirty is to review fixes submitted by others... > https://pharo.fogbugz.com/default.asp?pgx=LF&ixFilter=45 <https://pharo.fogbugz.com/default.asp?pgx=LF&ixFilter=45> > There are never enough hands there :) (my own action here fluctuates > from time to time) I will try to spend some time reviewing code. That is a good way to get exposed to things one does not even know they exist. > Did you look at Seaside? > Since you should be able to read french there is a nice tutorial: tinyBlog. In two days you can build a small web app > with a mongo back end. I have no looked at Seaside yet, I have not even read the corresponding chapter in UPBE. But I certainly will, eventually. The web is an essential part of society today. > Where are you located ? Paris, France. It did occur to me that the Pharo community does have a unusually large fraction of french people. But that is not a factor for me. Thanks again for all the kind words. I am sure this journey is going to be a lot of fun. :-)

Jan. 13, 2016

Re: [Pharo-users] Understanding the role of the sources file

by Dimitris Chloupis

Why the Cog VM is mentioned in my documentation is no accident. There is another VM that is called Stackless VM or old VM that was the VM before Cog that had no JIT and its a VM we still use for platforms that Cog VM does not currently run like Raspberry Pi, Android and I think iOS too. "But nowadays, JIT compiling byte-code to machine language are the norm rather than the exception, so I do not think it is worth mentioning." Definitely not the norm Python and Ruby VMs are not JIT, generally speaking JIT compilers are rare for Dynamic languages like Pharo. Python has PyPy which is a JIT VM but is nowhere as popular as Cpython. CPython people try to avoid JIT because it makes VM architecture much more complex. At least thats their argument. Another big advantage of Pharo is that it has luxury to come with a JIT included and well tested. The only popular JITs out there are Java's and .NET, dont know if Javascript V8 use JIT as well, but thats pretty much it. But bytecode is very popular indeed. On Wed, Jan 13, 2016 at 6:43 PM David Allouche <david(a)allouche.net> wrote: > On 13 Jan 2016, at 16:27, Dimitris Chloupis <kilon.alios(a)gmail.com> wrote: > > "The *virtual machine* (VM) provides the environment where the Pharo > system lives. It is different for each operating system and hardware > architecture, and runs as a machine language executable in the operating > system. It implements the details of managing memory, executing Pharo > byte-code, and communicating with the world outside of the Pharo system: > files, other operating system process, and the network." > > No the environment is the image, the VM is basically what its names says, > a machine emulated by software. The vast majority of tools, even the > language itself reside on the image. VM is there in order for the code to > be able to execute and to interface with the underlying Operating System. > You could completely modify the VM , for example move it to the JVM and > still the pharo enviroment would be intact. > > > That is indeed the idea I tried to convey by "where the Pharo system > lives", but I see how that can be misunderstood. However, I try to avoid > using "big words" like "abstraction". > > How about this? > > "The virtual machine (VM) provides the portable environment to execute > Pharo images. Its implementation needs to be different for each operating > system and hardware architecture, as it runs as a machine language > executable in the operating system. It implements the details of managing > memory, executing Pharo byte-code, and communicating with the world outside > of the Pharo system: files, other operating system process, and the > network. > > > "Hi Dimitris, > your formulation "...Pharo bytcode...and convert it to machine code..." > is insofar irritating to me as "convert it to machine code" would > suggest to me that a compiler is at work here. Davids "executing Pharo > byte-code" seems more understandable to me here." > > Thats correct its a compiler, a byte compiler, it compiles bytecode to > machine code and it does it while the code executes, this is why its called > JIT , which has the meaning of Just In Time compilation, meaning that > machine code is compiled just before the code is executed so several > optimizations can be applied that would not be known before the execution > of the code. Similar to JAVA's JIT compiler. > > Note here that a compiler is not just something that produces machine > code, a compiler for example can take one language and compile it to > another language. > > > That's technically true. But most readers will probably unconsciously > assume that a compiler is something that produces machine language. The > document should be careful to avoid misunderstandings caused by such common > assumptions. > > As for the JIT, that is totally an implementation detail, and I believe it > is only worth mentioning if you want to prevent the reader from assuming > that Pharo is slow because its VM executes byte-code. But nowadays, JIT > compiling byte-code to machine language are the norm rather than the > exception, so I do not think it is worth mentioning. > > > > On Wed, Jan 13, 2016 at 4:58 PM Werner Kassens <wkassens(a)libello.com> > wrote: > >> Hi Dimitris, >> your formulation "...Pharo bytcode...and convert it to machine code..." >> is insofar irritating to me as "convert it to machine code" would >> suggest to me that a compiler is at work here. Davids "executing Pharo >> byte-code" seems more understandable to me here. >> werner >> >> On 01/13/2016 02:22 PM, Dimitris Chloupis wrote: >> > I assume you have never read a an introduction to C++ then :D >> > >> > here is the final addition for the vm >> > >> > (Vm) is the only component that is different for each operating system. >> > The main purpose of the VM is to take Pharo bytcode that is generated >> > each time user accepts a piece of code and convert it to machine code in >> > order to be executed, but also to generally handle low level >> > functionality like interpreting code, handling OS events (mouse and >> > keyboard), calling C libraries etc. Pharo 4 comes with the Cog VM a very >> > fast JIT VM. >> > >> > I think its clear, precise and does not leave much room for confusion. >> > Personally I think its very important for the absolute begineer to have >> > strong foundations of understanding the fundamental of Pharo and not for >> > things to appear magical and "dont touch this". >> > >> > On Wed, Jan 13, 2016 at 2:54 PM Sven Van Caekenberghe <sven(a)stfx.eu >> > <mailto:sven@stfx.eu>> wrote: >> > >> > >> > > On 13 Jan 2016, at 13:42, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: >> > > >> > > I mentioned bytecode because I dont want the user to see at some >> > point bytecode and say "What the hell is that" I want the reader to >> > feel confident that at least understands the basic in Pharo. Also >> > very brief explanations about bytecode I have seen in similar python >> > tutorials. Obviously I dont want to go any deeper than that because >> > the user wont have to worry about the technical details on a daily >> > basis anyway. >> > > >> > > I agree that I could add a bit more on the VM description similar >> > to what you posted. I am curious though, wont even the interpreter >> > generate machine code in order to execute the code or does it use >> > existing machine code inside the VM binary ? >> > >> > No, a classic interpreter does not 'generate' machine code, it is >> > just a program that reads and executes bytes codes in a loop, the >> > interpreter 'is' machine code. >> > >> > No offence, but you see why I think it is important to not try to >> > use or explain too much complex concepts in the 1st chapter. >> > >> > Learning to program is hard. It should first be done abstractly. >> > Think about Scratch. The whole idea of Smalltalk is to create a >> > world of interacting objects. (Even byte code is not a necessary >> > concept at all, for example, in Pharo, you can compile (translate) >> > to AST and execute that, I believe. There are Smalltalk >> > implementations that compile directly to C or JavaScript). Hell, >> > even 'compile' is not necessary, just 'accept'. See ? >> > >> > > On Wed, Jan 13, 2016 at 2:25 PM Sven Van Caekenberghe >> > <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: >> > > Sounds about right. >> > > >> > > Now, I would swap 1 and 4, as the image is the most important >> > abstraction. >> > > >> > > There is also a bit too much emphasis on (byte|source)code. This >> > is already pretty technical (it assume you know what compilation is >> > and so on). But I understand it must be explained here, and you did >> > it well. >> > > >> > > However, I would start by saying that the image is a snapshot of >> > the object world in memory that is effectively a live Pharo system. >> > It contains everything that is available and that exists in Pharo. >> > This includes any objects that you created yourself, windows, >> > browsers, open debuggers, executing processes, all meta objects as >> > well as all representations of code. >> > > >> > > <sidenote> >> > > The fact that there is a sources and changes file is an >> > implementation artefact, not something fundamental. There are ideas >> > to change this in the future (but you do not have to mention that). >> > > </sidenote> >> > > >> > > Also, the VM not only executes code, it maintains the object >> > world, which includes the ability to load and save it from and to an >> > image. It creates a portable (cross platform) abstraction that >> > isolates the image from the particular details of the underlying >> > hardware and OS. In that role it implements the interface with the >> > outside world. I would mention that second part before mentioning >> > the code execution. >> > > >> > > The sentence "The purpose of the VM is to take Pharo bytcode that >> > is generated each time user accepts a piece of code and convert it >> > to machine code in order to be executed." is not 100% correct. It is >> > possible to execute the byte code without converting it. This is >> > called interpretation. JIT is a faster technique that includes >> > converting (some often used) byte code to machine code and caching >> that. >> > > >> > > I hope this helps (it is hard to write a 'definitive explanation' >> > as there are some many aspects to this and it depends on the >> > context/audience). >> > > >> > > > On 13 Jan 2016, at 12:58, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: >> > > > >> > > > So I am correct that the image does not store the source code, >> > and that the source code is stored in sources and changes. The only >> > diffirence is that the objects have a source variable that points to >> > the right place for finding the source code. >> > > > >> > > > This is the final text if you find anything incorrect please >> > correct me >> > > > >> > > > --------------- >> > > > >> > > > 1. The virtual machine (VM) is the only component that is >> > different for each operating system. The purpose of the VM is to >> > take Pharo bytcode that is generated each time user accepts a piece >> > of code and convert it to machine code in order to be executed. >> > Pharo 4 comes with the Cog VM a very fast JIT VM. The VM executable >> > is named: >> > > > >> > > > â¢ Pharo.exe for Windows; â¢ pharo for Linux ; and >> > > > >> > > > â¢ Pharo for OSX (inside a package also named Pharo.app). >> > > > The other components below are portable across operating >> > systems, and >> > > > >> > > > can be copied and run on any appropriate virtual machine. >> > > > >> > > > 2. The sources file contains source code for parts of Pharo >> > that donât change frequently. Sources file is important because the >> > image file format stores only the bytecode of live objects and not >> > their source code. Typically a new sources file is generated once >> > per major release of Pharo. For Pharo 4.0, this file is named >> > PharoV40.sources. >> > > > >> > > > 3. The changes file logs of all source code modifications since >> > the .sources file was generated. This facilitates a per method >> > history for diffs or re- verting.That means that even if you dont >> > manage to save the image file on a crash or you just forgot you can >> > recover your changes from this file. Each release provides a near >> > empty file named for the release, for example Pharo4.0.changes. >> > > > >> > > > 4. The image file provides a frozen in time snapshot of a >> > running Pharo system. This is the file where the Pharo bytecode is >> > stored and as such its a cross platform format. This is the heart of >> > Pharo, containing the live state of all objects in the system >> > (including classes and methods, since they are objects too). The >> > file is named for the release (like Pharo4.0.image). >> > > > >> > > > The .image and .changes files provided by a Pharo release are >> > the starting point for a live environment that you adapt to your >> > needs. Essentially the image file containes the compiler of the >> > language (not the VM) , the language parser, the IDE tools, many >> > libraries and acts a bit like a virtual Operation System that runs >> > on top of a Virtual Machine (VM), similarly to ISO files. >> > > > >> > > > As you work in Pharo, these files are modified, so you need to >> > make sure that they are writable. The .image and .changes files are >> > intimately linked and should always be kept together, with matching >> > base filenames. Never edit them directly with a text editor, as >> > .images holds your live object runtime memory, which indexes into >> > the .changes files for the source. It is a good idea to keep a >> > backup copy of the downloaded .image and .changes files so you can >> > always start from a fresh image and reload your code. However the >> > most efficient way for backing up code is to use a version control >> > system that will provide an easier and powerful way to back up and >> > track your changes. >> > > > >> > > > The four main component files above can be placed in the same >> > directory, although itâs also possible to put the Virtual Machine >> > and sources file in a separate directory where everyone has >> > read-only access to them. >> > > > >> > > > If more than one image file is present in the same directory >> > pharo will prompt you to choose an image file you want to load. >> > > > >> > > > Do whatever works best for your style of working and your >> > operating system. >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > On Wed, Jan 13, 2016 at 12:13 PM Sven Van Caekenberghe >> > <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: >> > > > >> > > > > On 13 Jan 2016, at 10:57, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: >> > > > > >> > > > > I was adding a short description to the UPBE about sources >> > file , I always thought that the sources file is the file that >> > contains the source code of the image because the image file itself >> > stores only the bytecode. >> > > > > >> > > > > However its just came to my attention that the sources file >> > does not contain code that is recently installed in the image. >> > > > > >> > > > > So how exactly the sources file works and what it is ? >> > > > >> > > > The main perspective is from the object point of view: methods >> > are just objects like everything else. In order to be executable >> > they know their byte codes (which might be JIT compiled on >> > execution, but that is an implementation detail) and they know their >> > source code. >> > > > >> > > > Today we would probably just store the source code strings in >> > the image (maybe compressed) as memory is pretty cheap. But way back >> > when Smalltalk started, that was not the case. So they decided to >> > map the source code out to files. >> > > > >> > > > So method source code is a magic string (RemoteString) that >> > points to some position in a file. There are 2 files in use: the >> > sources file and the changes file. >> > > > >> > > > The sources file is a kind of snapshot of the source code of >> > all methods at the point of release of a major new version. That is >> > why there is a Vxy in their name. The source file never changes once >> > created or renewed (a process called generating the sources, see >> > PharoSourcesCondenser). >> > > > >> > > > While developing and creating new versions of methods, the new >> > source code is appended to another file called the changes file, >> > much like a transaction log. This is also a safety mechanism to >> > recover 'lost' changes. >> > > > >> > > > The changes file can contain multiple versions of a method. >> > This can be reduced in size using a process called condensing the >> > changes, see PharoChangesCondenser. >> > > > >> > > > On a new release, the changes file will be (almost) empty. >> > > > >> > > > HTH, >> > > > >> > > > Sven >> > > > >> > > > >> > > > >> > > >> > > >> > >> > >> >>

Jan. 13, 2016

Re: [Pharo-users] Understanding the role of the sources file

by Dimitris Chloupis

It does not make as big difference as you think it does. First of all VM is an executable binary so its already in machine code format or else it would not run. The difference between the interpreter is that with the interpreter you already execute machine code without any need to generate it while JIT generates optimized machine code depending on the usage and case so it runs much faster than the machine code used by the interpreter . The bottom line is the same, machine code execution in both cases. Also from the link you provided its clear that the only way that codel wont be compiled to machine code is code that rarely used, code that you execute once and you forget about which you would not need to run fast anyway. In that case yes, the interpreter will be used. However there a ton of code that needs to run in a reparation of some sort , whether is drawing the GUI, examining an even, parsing a file , in most cases you will be using some kind of loop and in that case JIT will come to compile to machine code and you will see a very significant boost in speed depending on the case. But all that are implementations details which I dont want people to deal with, I only want the reader to have a very general idea what the VM and why Pharo needs it, I dont care about the specifics. On Wed, Jan 13, 2016 at 6:26 PM Ben Coman <btc(a)openinworld.com> wrote: > > On Wed, Jan 13, 2016 at 4:58 PM Werner Kassens <wkassens(a)libello.com> > wrote: > >> > >> Hi Dimitris, > >> your formulation "...Pharo bytcode...and convert it to machine code..." > >> is insofar irritating to me as "convert it to machine code" would > >> suggest to me that a compiler is at work here. Davids "executing Pharo > >> byte-code" seems more understandable to me here. > > On Wed, Jan 13, 2016 at 11:27 PM, Dimitris Chloupis > <kilon.alios(a)gmail.com> wrote: > > Thats correct its a compiler, a byte compiler, it compiles bytecode to > > machine code and it does it while the code executes, this is why its > called > > JIT , which has the meaning of Just In Time compilation, meaning that > > machine code is compiled just before the code is executed so several > > optimizations can be applied that would not be known before the > execution of > > the code. Similar to JAVA's JIT compiler. > > > > Note here that a compiler is not just something that produces machine > code, > > a compiler for example can take one language and compile it to another > > language. > > Indeed. The OpalCompiler takes Smalltalk and produces bytecode. > > However I think Sven and Werner were referring that much of Pharo code > is not JITd, but *merely* interpreted (IIUC). See section "Not so > smart questions" here... > > https://clementbera.wordpress.com/2014/01/09/the-sista-chronicles-i-an-intr… > > cheers -ben > > >> > >> On 01/13/2016 02:22 PM, Dimitris Chloupis wrote: > >> > I assume you have never read a an introduction to C++ then :D > >> > > >> > here is the final addition for the vm > >> > > >> > (Vm) is the only component that is different for each operating > system. > >> > The main purpose of the VM is to take Pharo bytcode that is generated > >> > each time user accepts a piece of code and convert it to machine code > in > >> > order to be executed, but also to generally handle low level > >> > functionality like interpreting code, handling OS events (mouse and > >> > keyboard), calling C libraries etc. Pharo 4 comes with the Cog VM a > very > >> > fast JIT VM. > >> > > >> > I think its clear, precise and does not leave much room for confusion. > >> > Personally I think its very important for the absolute begineer to > have > >> > strong foundations of understanding the fundamental of Pharo and not > for > >> > things to appear magical and "dont touch this". > >> > > >> > On Wed, Jan 13, 2016 at 2:54 PM Sven Van Caekenberghe <sven(a)stfx.eu > >> > <mailto:sven@stfx.eu>> wrote: > >> > > >> > > >> > > On 13 Jan 2016, at 13:42, Dimitris Chloupis > >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: > >> > > > >> > > I mentioned bytecode because I dont want the user to see at > some > >> > point bytecode and say "What the hell is that" I want the reader > to > >> > feel confident that at least understands the basic in Pharo. Also > >> > very brief explanations about bytecode I have seen in similar > python > >> > tutorials. Obviously I dont want to go any deeper than that > because > >> > the user wont have to worry about the technical details on a daily > >> > basis anyway. > >> > > > >> > > I agree that I could add a bit more on the VM description > similar > >> > to what you posted. I am curious though, wont even the interpreter > >> > generate machine code in order to execute the code or does it use > >> > existing machine code inside the VM binary ? > >> > > >> > No, a classic interpreter does not 'generate' machine code, it is > >> > just a program that reads and executes bytes codes in a loop, the > >> > interpreter 'is' machine code. > >> > > >> > No offence, but you see why I think it is important to not try to > >> > use or explain too much complex concepts in the 1st chapter. > >> > > >> > Learning to program is hard. It should first be done abstractly. > >> > Think about Scratch. The whole idea of Smalltalk is to create a > >> > world of interacting objects. (Even byte code is not a necessary > >> > concept at all, for example, in Pharo, you can compile (translate) > >> > to AST and execute that, I believe. There are Smalltalk > >> > implementations that compile directly to C or JavaScript). Hell, > >> > even 'compile' is not necessary, just 'accept'. See ? > >> > > >> > > On Wed, Jan 13, 2016 at 2:25 PM Sven Van Caekenberghe > >> > <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: > >> > > Sounds about right. > >> > > > >> > > Now, I would swap 1 and 4, as the image is the most important > >> > abstraction. > >> > > > >> > > There is also a bit too much emphasis on (byte|source)code. > This > >> > is already pretty technical (it assume you know what compilation > is > >> > and so on). But I understand it must be explained here, and you > did > >> > it well. > >> > > > >> > > However, I would start by saying that the image is a snapshot > of > >> > the object world in memory that is effectively a live Pharo > system. > >> > It contains everything that is available and that exists in Pharo. > >> > This includes any objects that you created yourself, windows, > >> > browsers, open debuggers, executing processes, all meta objects as > >> > well as all representations of code. > >> > > > >> > > <sidenote> > >> > > The fact that there is a sources and changes file is an > >> > implementation artefact, not something fundamental. There are > ideas > >> > to change this in the future (but you do not have to mention > that). > >> > > </sidenote> > >> > > > >> > > Also, the VM not only executes code, it maintains the object > >> > world, which includes the ability to load and save it from and to > an > >> > image. It creates a portable (cross platform) abstraction that > >> > isolates the image from the particular details of the underlying > >> > hardware and OS. In that role it implements the interface with the > >> > outside world. I would mention that second part before mentioning > >> > the code execution. > >> > > > >> > > The sentence "The purpose of the VM is to take Pharo bytcode > that > >> > is generated each time user accepts a piece of code and convert it > >> > to machine code in order to be executed." is not 100% correct. It > is > >> > possible to execute the byte code without converting it. This is > >> > called interpretation. JIT is a faster technique that includes > >> > converting (some often used) byte code to machine code and caching > >> > that. > >> > > > >> > > I hope this helps (it is hard to write a 'definitive > explanation' > >> > as there are some many aspects to this and it depends on the > >> > context/audience). > >> > > > >> > > > On 13 Jan 2016, at 12:58, Dimitris Chloupis > >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: > >> > > > > >> > > > So I am correct that the image does not store the source > code, > >> > and that the source code is stored in sources and changes. The > only > >> > diffirence is that the objects have a source variable that points > to > >> > the right place for finding the source code. > >> > > > > >> > > > This is the final text if you find anything incorrect please > >> > correct me > >> > > > > >> > > > --------------- > >> > > > > >> > > > 1. The virtual machine (VM) is the only component that is > >> > different for each operating system. The purpose of the VM is to > >> > take Pharo bytcode that is generated each time user accepts a > piece > >> > of code and convert it to machine code in order to be executed. > >> > Pharo 4 comes with the Cog VM a very fast JIT VM. The VM > executable > >> > is named: > >> > > > > >> > > > â¢ Pharo.exe for Windows; â¢ pharo for Linux ; and > >> > > > > >> > > > â¢ Pharo for OSX (inside a package also named Pharo.app). > >> > > > The other components below are portable across operating > >> > systems, and > >> > > > > >> > > > can be copied and run on any appropriate virtual machine. > >> > > > > >> > > > 2. The sources file contains source code for parts of Pharo > >> > that donât change frequently. Sources file is important because > the > >> > image file format stores only the bytecode of live objects and not > >> > their source code. Typically a new sources file is generated once > >> > per major release of Pharo. For Pharo 4.0, this file is named > >> > PharoV40.sources. > >> > > > > >> > > > 3. The changes file logs of all source code modifications > since > >> > the .sources file was generated. This facilitates a per method > >> > history for diffs or re- verting.That means that even if you dont > >> > manage to save the image file on a crash or you just forgot you > can > >> > recover your changes from this file. Each release provides a near > >> > empty file named for the release, for example Pharo4.0.changes. > >> > > > > >> > > > 4. The image file provides a frozen in time snapshot of a > >> > running Pharo system. This is the file where the Pharo bytecode is > >> > stored and as such its a cross platform format. This is the heart > of > >> > Pharo, containing the live state of all objects in the system > >> > (including classes and methods, since they are objects too). The > >> > file is named for the release (like Pharo4.0.image). > >> > > > > >> > > > The .image and .changes files provided by a Pharo release are > >> > the starting point for a live environment that you adapt to your > >> > needs. Essentially the image file containes the compiler of the > >> > language (not the VM) , the language parser, the IDE tools, many > >> > libraries and acts a bit like a virtual Operation System that runs > >> > on top of a Virtual Machine (VM), similarly to ISO files. > >> > > > > >> > > > As you work in Pharo, these files are modified, so you need > to > >> > make sure that they are writable. The .image and .changes files > are > >> > intimately linked and should always be kept together, with > matching > >> > base filenames. Never edit them directly with a text editor, as > >> > .images holds your live object runtime memory, which indexes into > >> > the .changes files for the source. It is a good idea to keep a > >> > backup copy of the downloaded .image and .changes files so you can > >> > always start from a fresh image and reload your code. However the > >> > most efficient way for backing up code is to use a version control > >> > system that will provide an easier and powerful way to back up and > >> > track your changes. > >> > > > > >> > > > The four main component files above can be placed in the same > >> > directory, although itâs also possible to put the Virtual Machine > >> > and sources file in a separate directory where everyone has > >> > read-only access to them. > >> > > > > >> > > > If more than one image file is present in the same directory > >> > pharo will prompt you to choose an image file you want to load. > >> > > > > >> > > > Do whatever works best for your style of working and your > >> > operating system. > >> > > > > >> > > > > >> > > > > >> > > > > >> > > > > >> > > > On Wed, Jan 13, 2016 at 12:13 PM Sven Van Caekenberghe > >> > <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: > >> > > > > >> > > > > On 13 Jan 2016, at 10:57, Dimitris Chloupis > >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: > >> > > > > > >> > > > > I was adding a short description to the UPBE about sources > >> > file , I always thought that the sources file is the file that > >> > contains the source code of the image because the image file > itself > >> > stores only the bytecode. > >> > > > > > >> > > > > However its just came to my attention that the sources file > >> > does not contain code that is recently installed in the image. > >> > > > > > >> > > > > So how exactly the sources file works and what it is ? > >> > > > > >> > > > The main perspective is from the object point of view: > methods > >> > are just objects like everything else. In order to be executable > >> > they know their byte codes (which might be JIT compiled on > >> > execution, but that is an implementation detail) and they know > their > >> > source code. > >> > > > > >> > > > Today we would probably just store the source code strings in > >> > the image (maybe compressed) as memory is pretty cheap. But way > back > >> > when Smalltalk started, that was not the case. So they decided to > >> > map the source code out to files. > >> > > > > >> > > > So method source code is a magic string (RemoteString) that > >> > points to some position in a file. There are 2 files in use: the > >> > sources file and the changes file. > >> > > > > >> > > > The sources file is a kind of snapshot of the source code of > >> > all methods at the point of release of a major new version. That > is > >> > why there is a Vxy in their name. The source file never changes > once > >> > created or renewed (a process called generating the sources, see > >> > PharoSourcesCondenser). > >> > > > > >> > > > While developing and creating new versions of methods, the > new > >> > source code is appended to another file called the changes file, > >> > much like a transaction log. This is also a safety mechanism to > >> > recover 'lost' changes. > >> > > > > >> > > > The changes file can contain multiple versions of a method. > >> > This can be reduced in size using a process called condensing the > >> > changes, see PharoChangesCondenser. > >> > > > > >> > > > On a new release, the changes file will be (almost) empty. > >> > > > > >> > > > HTH, > >> > > > > >> > > > Sven > >> > > > > >> > > > > >> > > > > >> > > > >> > > > >> > > >> > > >> > > > >

Jan. 13, 2016

Re: [Pharo-users] Understanding the role of the sources file

by David Allouche

> On 13 Jan 2016, at 16:27, Dimitris Chloupis <kilon.alios(a)gmail.com> wrote: > > "The virtual machine (VM) provides the environment where the Pharo system lives. It is different for each operating system and hardware architecture, and runs as a machine language executable in the operating system. It implements the details of managing memory, executing Pharo byte-code, and communicating with the world outside of the Pharo system: files, other operating system process, and the network." > > No the environment is the image, the VM is basically what its names says, a machine emulated by software. The vast majority of tools, even the language itself reside on the image. VM is there in order for the code to be able to execute and to interface with the underlying Operating System. You could completely modify the VM , for example move it to the JVM and still the pharo enviroment would be intact. That is indeed the idea I tried to convey by "where the Pharo system lives", but I see how that can be misunderstood. However, I try to avoid using "big words" like "abstraction". How about this? "The virtual machine (VM) provides the portable environment to execute Pharo images. Its implementation needs to be different for each operating system and hardware architecture, as it runs as a machine language executable in the operating system. It implements the details of managing memory, executing Pharo byte-code, and communicating with the world outside of the Pharo system: files, other operating system process, and the network. > "Hi Dimitris, > your formulation "...Pharo bytcode...and convert it to machine code..." > is insofar irritating to me as "convert it to machine code" would > suggest to me that a compiler is at work here. Davids "executing Pharo > byte-code" seems more understandable to me here." > > Thats correct its a compiler, a byte compiler, it compiles bytecode to machine code and it does it while the code executes, this is why its called JIT , which has the meaning of Just In Time compilation, meaning that machine code is compiled just before the code is executed so several optimizations can be applied that would not be known before the execution of the code. Similar to JAVA's JIT compiler. > > Note here that a compiler is not just something that produces machine code, a compiler for example can take one language and compile it to another language. That's technically true. But most readers will probably unconsciously assume that a compiler is something that produces machine language. The document should be careful to avoid misunderstandings caused by such common assumptions. As for the JIT, that is totally an implementation detail, and I believe it is only worth mentioning if you want to prevent the reader from assuming that Pharo is slow because its VM executes byte-code. But nowadays, JIT compiling byte-code to machine language are the norm rather than the exception, so I do not think it is worth mentioning. > > On Wed, Jan 13, 2016 at 4:58 PM Werner Kassens <wkassens(a)libello.com <mailto:wkassens@libello.com>> wrote: > Hi Dimitris, > your formulation "...Pharo bytcode...and convert it to machine code..." > is insofar irritating to me as "convert it to machine code" would > suggest to me that a compiler is at work here. Davids "executing Pharo > byte-code" seems more understandable to me here. > werner > > On 01/13/2016 02:22 PM, Dimitris Chloupis wrote: > > I assume you have never read a an introduction to C++ then :D > > > > here is the final addition for the vm > > > > (Vm) is the only component that is different for each operating system. > > The main purpose of the VM is to take Pharo bytcode that is generated > > each time user accepts a piece of code and convert it to machine code in > > order to be executed, but also to generally handle low level > > functionality like interpreting code, handling OS events (mouse and > > keyboard), calling C libraries etc. Pharo 4 comes with the Cog VM a very > > fast JIT VM. > > > > I think its clear, precise and does not leave much room for confusion. > > Personally I think its very important for the absolute begineer to have > > strong foundations of understanding the fundamental of Pharo and not for > > things to appear magical and "dont touch this". > > > > On Wed, Jan 13, 2016 at 2:54 PM Sven Van Caekenberghe <sven(a)stfx.eu <mailto:sven@stfx.eu> > > <mailto:sven@stfx.eu <mailto:sven@stfx.eu>>> wrote: > > > > > > > On 13 Jan 2016, at 13:42, Dimitris Chloupis > > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com> <mailto:kilon.alios@gmail.com <mailto:kilon.alios@gmail.com>>> wrote: > > > > > > I mentioned bytecode because I dont want the user to see at some > > point bytecode and say "What the hell is that" I want the reader to > > feel confident that at least understands the basic in Pharo. Also > > very brief explanations about bytecode I have seen in similar python > > tutorials. Obviously I dont want to go any deeper than that because > > the user wont have to worry about the technical details on a daily > > basis anyway. > > > > > > I agree that I could add a bit more on the VM description similar > > to what you posted. I am curious though, wont even the interpreter > > generate machine code in order to execute the code or does it use > > existing machine code inside the VM binary ? > > > > No, a classic interpreter does not 'generate' machine code, it is > > just a program that reads and executes bytes codes in a loop, the > > interpreter 'is' machine code. > > > > No offence, but you see why I think it is important to not try to > > use or explain too much complex concepts in the 1st chapter. > > > > Learning to program is hard. It should first be done abstractly. > > Think about Scratch. The whole idea of Smalltalk is to create a > > world of interacting objects. (Even byte code is not a necessary > > concept at all, for example, in Pharo, you can compile (translate) > > to AST and execute that, I believe. There are Smalltalk > > implementations that compile directly to C or JavaScript). Hell, > > even 'compile' is not necessary, just 'accept'. See ? > > > > > On Wed, Jan 13, 2016 at 2:25 PM Sven Van Caekenberghe > > <sven(a)stfx.eu <mailto:sven@stfx.eu> <mailto:sven@stfx.eu <mailto:sven@stfx.eu>>> wrote: > > > Sounds about right. > > > > > > Now, I would swap 1 and 4, as the image is the most important > > abstraction. > > > > > > There is also a bit too much emphasis on (byte|source)code. This > > is already pretty technical (it assume you know what compilation is > > and so on). But I understand it must be explained here, and you did > > it well. > > > > > > However, I would start by saying that the image is a snapshot of > > the object world in memory that is effectively a live Pharo system. > > It contains everything that is available and that exists in Pharo. > > This includes any objects that you created yourself, windows, > > browsers, open debuggers, executing processes, all meta objects as > > well as all representations of code. > > > > > > <sidenote> > > > The fact that there is a sources and changes file is an > > implementation artefact, not something fundamental. There are ideas > > to change this in the future (but you do not have to mention that). > > > </sidenote> > > > > > > Also, the VM not only executes code, it maintains the object > > world, which includes the ability to load and save it from and to an > > image. It creates a portable (cross platform) abstraction that > > isolates the image from the particular details of the underlying > > hardware and OS. In that role it implements the interface with the > > outside world. I would mention that second part before mentioning > > the code execution. > > > > > > The sentence "The purpose of the VM is to take Pharo bytcode that > > is generated each time user accepts a piece of code and convert it > > to machine code in order to be executed." is not 100% correct. It is > > possible to execute the byte code without converting it. This is > > called interpretation. JIT is a faster technique that includes > > converting (some often used) byte code to machine code and caching that. > > > > > > I hope this helps (it is hard to write a 'definitive explanation' > > as there are some many aspects to this and it depends on the > > context/audience). > > > > > > > On 13 Jan 2016, at 12:58, Dimitris Chloupis > > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com> <mailto:kilon.alios@gmail.com <mailto:kilon.alios@gmail.com>>> wrote: > > > > > > > > So I am correct that the image does not store the source code, > > and that the source code is stored in sources and changes. The only > > diffirence is that the objects have a source variable that points to > > the right place for finding the source code. > > > > > > > > This is the final text if you find anything incorrect please > > correct me > > > > > > > > --------------- > > > > > > > > 1. The virtual machine (VM) is the only component that is > > different for each operating system. The purpose of the VM is to > > take Pharo bytcode that is generated each time user accepts a piece > > of code and convert it to machine code in order to be executed. > > Pharo 4 comes with the Cog VM a very fast JIT VM. The VM executable > > is named: > > > > > > > > â¢ Pharo.exe for Windows; â¢ pharo for Linux ; and > > > > > > > > â¢ Pharo for OSX (inside a package also named Pharo.app). > > > > The other components below are portable across operating > > systems, and > > > > > > > > can be copied and run on any appropriate virtual machine. > > > > > > > > 2. The sources file contains source code for parts of Pharo > > that donât change frequently. Sources file is important because the > > image file format stores only the bytecode of live objects and not > > their source code. Typically a new sources file is generated once > > per major release of Pharo. For Pharo 4.0, this file is named > > PharoV40.sources. > > > > > > > > 3. The changes file logs of all source code modifications since > > the .sources file was generated. This facilitates a per method > > history for diffs or re- verting.That means that even if you dont > > manage to save the image file on a crash or you just forgot you can > > recover your changes from this file. Each release provides a near > > empty file named for the release, for example Pharo4.0.changes. > > > > > > > > 4. The image file provides a frozen in time snapshot of a > > running Pharo system. This is the file where the Pharo bytecode is > > stored and as such its a cross platform format. This is the heart of > > Pharo, containing the live state of all objects in the system > > (including classes and methods, since they are objects too). The > > file is named for the release (like Pharo4.0.image). > > > > > > > > The .image and .changes files provided by a Pharo release are > > the starting point for a live environment that you adapt to your > > needs. Essentially the image file containes the compiler of the > > language (not the VM) , the language parser, the IDE tools, many > > libraries and acts a bit like a virtual Operation System that runs > > on top of a Virtual Machine (VM), similarly to ISO files. > > > > > > > > As you work in Pharo, these files are modified, so you need to > > make sure that they are writable. The .image and .changes files are > > intimately linked and should always be kept together, with matching > > base filenames. Never edit them directly with a text editor, as > > .images holds your live object runtime memory, which indexes into > > the .changes files for the source. It is a good idea to keep a > > backup copy of the downloaded .image and .changes files so you can > > always start from a fresh image and reload your code. However the > > most efficient way for backing up code is to use a version control > > system that will provide an easier and powerful way to back up and > > track your changes. > > > > > > > > The four main component files above can be placed in the same > > directory, although itâs also possible to put the Virtual Machine > > and sources file in a separate directory where everyone has > > read-only access to them. > > > > > > > > If more than one image file is present in the same directory > > pharo will prompt you to choose an image file you want to load. > > > > > > > > Do whatever works best for your style of working and your > > operating system. > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Jan 13, 2016 at 12:13 PM Sven Van Caekenberghe > > <sven(a)stfx.eu <mailto:sven@stfx.eu> <mailto:sven@stfx.eu <mailto:sven@stfx.eu>>> wrote: > > > > > > > > > On 13 Jan 2016, at 10:57, Dimitris Chloupis > > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com> <mailto:kilon.alios@gmail.com <mailto:kilon.alios@gmail.com>>> wrote: > > > > > > > > > > I was adding a short description to the UPBE about sources > > file , I always thought that the sources file is the file that > > contains the source code of the image because the image file itself > > stores only the bytecode. > > > > > > > > > > However its just came to my attention that the sources file > > does not contain code that is recently installed in the image. > > > > > > > > > > So how exactly the sources file works and what it is ? > > > > > > > > The main perspective is from the object point of view: methods > > are just objects like everything else. In order to be executable > > they know their byte codes (which might be JIT compiled on > > execution, but that is an implementation detail) and they know their > > source code. > > > > > > > > Today we would probably just store the source code strings in > > the image (maybe compressed) as memory is pretty cheap. But way back > > when Smalltalk started, that was not the case. So they decided to > > map the source code out to files. > > > > > > > > So method source code is a magic string (RemoteString) that > > points to some position in a file. There are 2 files in use: the > > sources file and the changes file. > > > > > > > > The sources file is a kind of snapshot of the source code of > > all methods at the point of release of a major new version. That is > > why there is a Vxy in their name. The source file never changes once > > created or renewed (a process called generating the sources, see > > PharoSourcesCondenser). > > > > > > > > While developing and creating new versions of methods, the new > > source code is appended to another file called the changes file, > > much like a transaction log. This is also a safety mechanism to > > recover 'lost' changes. > > > > > > > > The changes file can contain multiple versions of a method. > > This can be reduced in size using a process called condensing the > > changes, see PharoChangesCondenser. > > > > > > > > On a new release, the changes file will be (almost) empty. > > > > > > > > HTH, > > > > > > > > Sven > > > > > > > > > > > > > > > > > > > > > > >

Jan. 13, 2016

Re: [Pharo-users] I am David Allouche, let me introduce myself.

by Serge Stinckwich

Welcome in the community David ! Where are you located ? Regards, On Sun, Jan 10, 2016 at 10:37 PM, David Allouche <david(a)allouche.net> wrote: > Hello folks. > > Some people have already seen me on Twitter and Slack, but I believe there > might be some people on the mailing list that did not see those > conversations. > > As I have done on Slack, I am writing this introduction so people have an > idea where I come from and what is my business with Pharo. > > I am a professional programmer. My current job is tech on a small company I > run with two associates (by the way, we are hiring a good Python web dev > with a passion for good code). The product is a SaaS web application for > recruiters. They call that an Application Tracking System, it is a workflow, > communication and archival system for job applications and candidates. > > I started programming 25 years ago with HyperCard, and since I have at least > played with Pascal, C, Prograph, asm68k, HP-48 (RPL, Saturn asm), Java, > bash, C++, LaTeX, XSLT, Delphi, Scheme, elisp, JavaScript. > > I have contributed to GNU TeXmacs where I made important contributinos > during about 2 years, as I completed by training as an software engineer, > and worked at CNRS in Rennes. Then I got involved in GNU Arch (wrote a > Python driver), Bazaar (bzr scm) where I worked with the founding team at > Canonical while working on the version control aspect of launchpad.net. > After that, I had mostly no contribution to free software, working on > financial modeling at a bank and then on my current business. I made a > presentation on SQLAlchemy at PyCon.fr 2015. > > I am a fan Design Patterns (GoF) and the Refactoring book. My mentor at > Canonical (Robert Collins) is heavily influenced by Smalltalk and championed > XP there. I always had strong interests in software systems design, > programming language design, typography, and user interface design. I feel > strongly for the concept of software craftsmanship. > > My current job is nice, good pay, lots of independence ; after 6 years > working on the same project, I need some fresh intellectual stimulation. And > I was recently impressed by the presentation "Nothing is Something", by > Sandi Metz, who is heavily influenced by Smalltalk. > > http://confreaks.tv/videos/bathruby2015-nothing-is-something > > So, I here I came, bumbling my way around the system, looking for > intellectual stimulation, and for a way to make a positive contribution. > > I was very impressed by the nice welcome I have received. And I see there is > lots of useful work to do here. > > So that's where I come from when you see me chipping in the conversation > here. > > Regards. -- Serge Stinckwich UCBN & UMI UMMISCO 209 (IRD/UPMC) Every DSL ends up being Smalltalk http://www.doesnotunderstand.org/

Jan. 13, 2016

Re: [Pharo-users] Understanding the role of the sources file

by Ben Coman

> On Wed, Jan 13, 2016 at 4:58 PM Werner Kassens <wkassens(a)libello.com> wrote: >> >> Hi Dimitris, >> your formulation "...Pharo bytcode...and convert it to machine code..." >> is insofar irritating to me as "convert it to machine code" would >> suggest to me that a compiler is at work here. Davids "executing Pharo >> byte-code" seems more understandable to me here. On Wed, Jan 13, 2016 at 11:27 PM, Dimitris Chloupis <kilon.alios(a)gmail.com> wrote: > Thats correct its a compiler, a byte compiler, it compiles bytecode to > machine code and it does it while the code executes, this is why its called > JIT , which has the meaning of Just In Time compilation, meaning that > machine code is compiled just before the code is executed so several > optimizations can be applied that would not be known before the execution of > the code. Similar to JAVA's JIT compiler. > > Note here that a compiler is not just something that produces machine code, > a compiler for example can take one language and compile it to another > language. Indeed. The OpalCompiler takes Smalltalk and produces bytecode. However I think Sven and Werner were referring that much of Pharo code is not JITd, but *merely* interpreted (IIUC). See section "Not so smart questions" here... https://clementbera.wordpress.com/2014/01/09/the-sista-chronicles-i-an-intr… cheers -ben >> >> On 01/13/2016 02:22 PM, Dimitris Chloupis wrote: >> > I assume you have never read a an introduction to C++ then :D >> > >> > here is the final addition for the vm >> > >> > (Vm) is the only component that is different for each operating system. >> > The main purpose of the VM is to take Pharo bytcode that is generated >> > each time user accepts a piece of code and convert it to machine code in >> > order to be executed, but also to generally handle low level >> > functionality like interpreting code, handling OS events (mouse and >> > keyboard), calling C libraries etc. Pharo 4 comes with the Cog VM a very >> > fast JIT VM. >> > >> > I think its clear, precise and does not leave much room for confusion. >> > Personally I think its very important for the absolute begineer to have >> > strong foundations of understanding the fundamental of Pharo and not for >> > things to appear magical and "dont touch this". >> > >> > On Wed, Jan 13, 2016 at 2:54 PM Sven Van Caekenberghe <sven(a)stfx.eu >> > <mailto:sven@stfx.eu>> wrote: >> > >> > >> > > On 13 Jan 2016, at 13:42, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: >> > > >> > > I mentioned bytecode because I dont want the user to see at some >> > point bytecode and say "What the hell is that" I want the reader to >> > feel confident that at least understands the basic in Pharo. Also >> > very brief explanations about bytecode I have seen in similar python >> > tutorials. Obviously I dont want to go any deeper than that because >> > the user wont have to worry about the technical details on a daily >> > basis anyway. >> > > >> > > I agree that I could add a bit more on the VM description similar >> > to what you posted. I am curious though, wont even the interpreter >> > generate machine code in order to execute the code or does it use >> > existing machine code inside the VM binary ? >> > >> > No, a classic interpreter does not 'generate' machine code, it is >> > just a program that reads and executes bytes codes in a loop, the >> > interpreter 'is' machine code. >> > >> > No offence, but you see why I think it is important to not try to >> > use or explain too much complex concepts in the 1st chapter. >> > >> > Learning to program is hard. It should first be done abstractly. >> > Think about Scratch. The whole idea of Smalltalk is to create a >> > world of interacting objects. (Even byte code is not a necessary >> > concept at all, for example, in Pharo, you can compile (translate) >> > to AST and execute that, I believe. There are Smalltalk >> > implementations that compile directly to C or JavaScript). Hell, >> > even 'compile' is not necessary, just 'accept'. See ? >> > >> > > On Wed, Jan 13, 2016 at 2:25 PM Sven Van Caekenberghe >> > <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: >> > > Sounds about right. >> > > >> > > Now, I would swap 1 and 4, as the image is the most important >> > abstraction. >> > > >> > > There is also a bit too much emphasis on (byte|source)code. This >> > is already pretty technical (it assume you know what compilation is >> > and so on). But I understand it must be explained here, and you did >> > it well. >> > > >> > > However, I would start by saying that the image is a snapshot of >> > the object world in memory that is effectively a live Pharo system. >> > It contains everything that is available and that exists in Pharo. >> > This includes any objects that you created yourself, windows, >> > browsers, open debuggers, executing processes, all meta objects as >> > well as all representations of code. >> > > >> > > <sidenote> >> > > The fact that there is a sources and changes file is an >> > implementation artefact, not something fundamental. There are ideas >> > to change this in the future (but you do not have to mention that). >> > > </sidenote> >> > > >> > > Also, the VM not only executes code, it maintains the object >> > world, which includes the ability to load and save it from and to an >> > image. It creates a portable (cross platform) abstraction that >> > isolates the image from the particular details of the underlying >> > hardware and OS. In that role it implements the interface with the >> > outside world. I would mention that second part before mentioning >> > the code execution. >> > > >> > > The sentence "The purpose of the VM is to take Pharo bytcode that >> > is generated each time user accepts a piece of code and convert it >> > to machine code in order to be executed." is not 100% correct. It is >> > possible to execute the byte code without converting it. This is >> > called interpretation. JIT is a faster technique that includes >> > converting (some often used) byte code to machine code and caching >> > that. >> > > >> > > I hope this helps (it is hard to write a 'definitive explanation' >> > as there are some many aspects to this and it depends on the >> > context/audience). >> > > >> > > > On 13 Jan 2016, at 12:58, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: >> > > > >> > > > So I am correct that the image does not store the source code, >> > and that the source code is stored in sources and changes. The only >> > diffirence is that the objects have a source variable that points to >> > the right place for finding the source code. >> > > > >> > > > This is the final text if you find anything incorrect please >> > correct me >> > > > >> > > > --------------- >> > > > >> > > > 1. The virtual machine (VM) is the only component that is >> > different for each operating system. The purpose of the VM is to >> > take Pharo bytcode that is generated each time user accepts a piece >> > of code and convert it to machine code in order to be executed. >> > Pharo 4 comes with the Cog VM a very fast JIT VM. The VM executable >> > is named: >> > > > >> > > > â¢ Pharo.exe for Windows; â¢ pharo for Linux ; and >> > > > >> > > > â¢ Pharo for OSX (inside a package also named Pharo.app). >> > > > The other components below are portable across operating >> > systems, and >> > > > >> > > > can be copied and run on any appropriate virtual machine. >> > > > >> > > > 2. The sources file contains source code for parts of Pharo >> > that donât change frequently. Sources file is important because the >> > image file format stores only the bytecode of live objects and not >> > their source code. Typically a new sources file is generated once >> > per major release of Pharo. For Pharo 4.0, this file is named >> > PharoV40.sources. >> > > > >> > > > 3. The changes file logs of all source code modifications since >> > the .sources file was generated. This facilitates a per method >> > history for diffs or re- verting.That means that even if you dont >> > manage to save the image file on a crash or you just forgot you can >> > recover your changes from this file. Each release provides a near >> > empty file named for the release, for example Pharo4.0.changes. >> > > > >> > > > 4. The image file provides a frozen in time snapshot of a >> > running Pharo system. This is the file where the Pharo bytecode is >> > stored and as such its a cross platform format. This is the heart of >> > Pharo, containing the live state of all objects in the system >> > (including classes and methods, since they are objects too). The >> > file is named for the release (like Pharo4.0.image). >> > > > >> > > > The .image and .changes files provided by a Pharo release are >> > the starting point for a live environment that you adapt to your >> > needs. Essentially the image file containes the compiler of the >> > language (not the VM) , the language parser, the IDE tools, many >> > libraries and acts a bit like a virtual Operation System that runs >> > on top of a Virtual Machine (VM), similarly to ISO files. >> > > > >> > > > As you work in Pharo, these files are modified, so you need to >> > make sure that they are writable. The .image and .changes files are >> > intimately linked and should always be kept together, with matching >> > base filenames. Never edit them directly with a text editor, as >> > .images holds your live object runtime memory, which indexes into >> > the .changes files for the source. It is a good idea to keep a >> > backup copy of the downloaded .image and .changes files so you can >> > always start from a fresh image and reload your code. However the >> > most efficient way for backing up code is to use a version control >> > system that will provide an easier and powerful way to back up and >> > track your changes. >> > > > >> > > > The four main component files above can be placed in the same >> > directory, although itâs also possible to put the Virtual Machine >> > and sources file in a separate directory where everyone has >> > read-only access to them. >> > > > >> > > > If more than one image file is present in the same directory >> > pharo will prompt you to choose an image file you want to load. >> > > > >> > > > Do whatever works best for your style of working and your >> > operating system. >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > On Wed, Jan 13, 2016 at 12:13 PM Sven Van Caekenberghe >> > <sven(a)stfx.eu <mailto:sven@stfx.eu>> wrote: >> > > > >> > > > > On 13 Jan 2016, at 10:57, Dimitris Chloupis >> > <kilon.alios(a)gmail.com <mailto:kilon.alios@gmail.com>> wrote: >> > > > > >> > > > > I was adding a short description to the UPBE about sources >> > file , I always thought that the sources file is the file that >> > contains the source code of the image because the image file itself >> > stores only the bytecode. >> > > > > >> > > > > However its just came to my attention that the sources file >> > does not contain code that is recently installed in the image. >> > > > > >> > > > > So how exactly the sources file works and what it is ? >> > > > >> > > > The main perspective is from the object point of view: methods >> > are just objects like everything else. In order to be executable >> > they know their byte codes (which might be JIT compiled on >> > execution, but that is an implementation detail) and they know their >> > source code. >> > > > >> > > > Today we would probably just store the source code strings in >> > the image (maybe compressed) as memory is pretty cheap. But way back >> > when Smalltalk started, that was not the case. So they decided to >> > map the source code out to files. >> > > > >> > > > So method source code is a magic string (RemoteString) that >> > points to some position in a file. There are 2 files in use: the >> > sources file and the changes file. >> > > > >> > > > The sources file is a kind of snapshot of the source code of >> > all methods at the point of release of a major new version. That is >> > why there is a Vxy in their name. The source file never changes once >> > created or renewed (a process called generating the sources, see >> > PharoSourcesCondenser). >> > > > >> > > > While developing and creating new versions of methods, the new >> > source code is appended to another file called the changes file, >> > much like a transaction log. This is also a safety mechanism to >> > recover 'lost' changes. >> > > > >> > > > The changes file can contain multiple versions of a method. >> > This can be reduced in size using a process called condensing the >> > changes, see PharoChangesCondenser. >> > > > >> > > > On a new release, the changes file will be (almost) empty. >> > > > >> > > > HTH, >> > > > >> > > > Sven >> > > > >> > > > >> > > > >> > > >> > > >> > >> > >> >

Jan. 13, 2016