- Pharo-users - lists.pharo.org

Re: [Pharo-users] BlockClosure

by Sven Van Caekenberghe

Hi Johan, That is nice indeed. It is good to see that you have fun learning Pharo Smalltalk. Can you do it ? Of course, you can do what you want, Pharo Smalltalk is a highly flexible environment. Key to its simplicity are its ultra simple syntax which hits a magical optimum between simplicity and capability (full syntax on a postcard). With just messages and block, you can express almost anything (one limitation is that there are no macros). Part of that is (for me at least), left to right evaluation/reading - trying to change that 'hurts'. Binary operators are useful and even necessary, but the problem with totally new uses is that readers won't understand them. Being a bit more verbose helps, in my opinion. You might also be interested in the following: Lambda Calculus in Pharo Yes, the Y Combinator is useful in normal programs https://medium.com/concerning-pharo/lambda-calculus-in-pharo-a4a571869594 Regards, Sven > On 23 Oct 2019, at 15:12, main <johan_forsberg_86(a)hotmail.com> wrote: > > Hi again! > > Just putting it out there for anyone interested. > > What I did was define the following in Object: > > |> aBlock > ^ [ :x | x => self => aBlock ] > > and also: > > => msg > ^ msg value: self > > > This enabled me to compose like this (I know I probably violate every rule > in the book, whatever ): > > f := [ :x | x + 100 ]. > g := [ :x | x + 20 ]. > h := [ :x | x + 3 ]. > > 0 => (f |> g |> h). 123 > > Also tried using ~: > > 0 => (f ~ g ~ h). 123 > > It's just a matter of taste I guess, but for me it warms my heart > > > > -- > Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html >

Oct. 23, 2019

Re: [Pharo-users] BlockClosure

by Steffen MÃ¤rcker

Looks nice! Just my two cents. To make function comopostion work with multiple aruments, I implemented * as: BlockClosure class>>* first ^ComposedFunction first: first second: self And use a dedicated class to make multiple arguments work: ComposedFunction>>value: arg ^second value: (first value: arg) ComposedFunction>>value: arg1 value: arg2 ^second value: (first value: arg1 value arg2) Then, we can write: [:x | x factorial ] * [:x :y | x + y] value: 1 value: 2 (I usually use the mathematical compostion operator, wich evalutes from right to left.) However, it is often convenient to interchange Symbols and Blocks, e.g., the above can be rewritten as #factorial * #+ value: 1 value: 2 That requires to implement the * operator on symbols, too. And depending on your Smalltalk implemenation, you may have to implement the evaluation protocol on symbols. Best, Steffen Am .10.2019, 15:12 Uhr, schrieb main <johan_forsberg_86(a)hotmail.com>: > Hi again! > > Just putting it out there for anyone interested. > > What I did was define the following in Object: > > |> aBlock > ^ [ :x | x => self => aBlock ] > > and also: > > => msg > ^ msg value: self > > > This enabled me to compose like this (I know I probably violate every > rule > in the book, whatever ): > > f := [ :x | x + 100 ]. > g := [ :x | x + 20 ]. > h := [ :x | x + 3 ]. > > 0 => (f |> g |> h). 123 > > Also tried using ~: > > 0 => (f ~ g ~ h). 123 > > It's just a matter of taste I guess, but for me it warms my heart > > > > -- > Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Oct. 23, 2019

Re: [Pharo-users] BlockClosure

by main

Hi again! Just putting it out there for anyone interested. What I did was define the following in Object: |> aBlock ^ [ :x | x => self => aBlock ] and also: => msg ^ msg value: self This enabled me to compose like this (I know I probably violate every rule in the book, whatever ): f := [ :x | x + 100 ]. g := [ :x | x + 20 ]. h := [ :x | x + 3 ]. 0 => (f |> g |> h). 123 Also tried using ~: 0 => (f ~ g ~ h). 123 It's just a matter of taste I guess, but for me it warms my heart -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Oct. 23, 2019

Re: [Pharo-users] BlockClosure

by phil＠highoctane.be

On Wed, 23 Oct 2019, 14:25 Kasper Osterbye, <kasper.osterbye(a)gmail.com> wrote: > On Wed, Oct 23, 2019 at 2:21 PM phil(a)highoctane.be <phil(a)highoctane.be> > wrote: > >> It is like Object>>in: aBlock no? >> > Yes. > > But because it is an operator, you can write "obj => block => block => > block". > You can not write "obj in: block in: block in: block", because smalltalk > will think it is a selector named "in:in:in:". > Indeed. I would still use in: with parentheses instead of introducing a new (albeit cool) operator. Phil > Best, > > Kasper >

Oct. 23, 2019

Rocking Smalltalk

by Richard Kenneth Eng

https://youtu.be/-uTzhRLcWC4 A rock video for the Smalltalk programming language.

Oct. 23, 2019

Re: [Pharo-users] BlockClosure

by Kasper Osterbye

On Wed, Oct 23, 2019 at 2:21 PM phil(a)highoctane.be <phil(a)highoctane.be> wrote: > It is like Object>>in: aBlock no? > Yes. But because it is an operator, you can write "obj => block => block => block". You can not write "obj in: block in: block in: block", because smalltalk will think it is a selector named "in:in:in:". Best, Kasper

Oct. 23, 2019

Re: [Pharo-users] BlockClosure

by phil＠highoctane.be

It is like Object>>in: aBlock no? On Wed, 23 Oct 2019, 10:27 Kasper Osterbye, <kasper.osterbye(a)gmail.com> wrote: > You can define a method "=>" in Object as: > > => aBlock > ^ aBlock value: self > > That would allow you to write expressions like this: > 7 => [ :x | x+3 ] => [ :x| x*3 ], > > if you further define "=>" in Array as: > > => aBlock > ^ aBlock valueWithArguments: self > > > you are able to write your example: > (([ :f :g | [ :x | f (g x) ] ]) [:x | x + 1] [:x | x - 1]) 5 > > as: > > 5 => ({ [:x | x + 1]. [:x | x - 1]} => [ :f :g | [ :x | x => g =>f ] ]). > > It reads from left to right where yours is the usual Arabic (right to > left) favoured in functional style. > > >

Oct. 23, 2019

Re: [Pharo-users] BlockClosure

by main

That's great! Thanks! Now I will write Pharo forever I first thought of implementing the doesNotUnderstand, but I think this is a better way! -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Oct. 23, 2019

Re: [Pharo-users] BlockClosure

by Kasper Osterbye

You can define a method "=>" in Object as: => aBlock ^ aBlock value: self That would allow you to write expressions like this: 7 => [ :x | x+3 ] => [ :x| x*3 ], if you further define "=>" in Array as: => aBlock ^ aBlock valueWithArguments: self you are able to write your example: (([ :f :g | [ :x | f (g x) ] ]) [:x | x + 1] [:x | x - 1]) 5 as: 5 => ({ [:x | x + 1]. [:x | x - 1]} => [ :f :g | [ :x | x => g =>f ] ]). It reads from left to right where yours is the usual Arabic (right to left) favoured in functional style.

Oct. 23, 2019

Re: [Pharo-users] BlockClosure

by pmissech

Hi, The first part could be done, but with limitations. - you won't be able to value it with anything but variables names - those variables cannot have the same name as a method of BlockClosure - I don't think this can be implemented by default in Pharo, as it is kinda "dangerous" - might be unreliable, i don't know how stable Context is. ( For my own experiments, I have some problem with P7, but my stuff work fine on P8) You'd have to implement something like: BlockClosure >> DoesNotUnderstand: aMessage Â Â Â valueOfSelector := self outerContext at: aMessage selector ifAbsent:[ ^ super doesNotUnderstand "The variable isn't found in the context, so it's a real DNU "]. Â Â Â self valueWithArguments: valueOfSelector asArray "allows us to have several arguments" So if you did: aVariable := 3. [:x | x + 3] aVariable. The block would say it didn't understand the message aVariable, and you'd perform it in the doesNotUnderstand hook you just override. I guess it'd be something similar for the second part of your question, but i'm pretty sure it becomes unreadable rather quickly ËË PS: I didn't test this, but it's something in that spirit. the context access might not be outerContext. Pierre. On 23/10/2019 09:22, main wrote: > Hello fellow Pharoians (?) from a lonely Swede. > > I just found out about Pharo (and Smalltalk) two days ago and I'm already > loving it :) > However, there is a behavior I would like to change, or be enlightened about > how it could be done. > > As I understand it (bear with me) BlockClosure from Kernel-Methods does not > understand (by default?) how to respond to an "anonymous object" (no message > name). > > Is there any way this could be implemented? I'll post an example soon > (I currently use both Pharo 7 and 8) > > If I write the following: > > [:x | x + 1] value: 3 > > and evaluate it, I get the expected result, which is 4. > > That's nice. > > What I would really like is to be able to just send 3 to BlockClosure and > make it repond as above. > > Like this: > > [:x | x + 1] 3 > > or like this: > > 3 [:x | x + 1] > > Would this be possible? > > ----------------------- > > Also as a bonus, would it be possible to use this for "function > composition", "Block composition" or similar? > > Example of composition: > > [ :f :g | [ :x | f value: (g value: x) ] ] > > I could use this construct like this for example: > > (([ :f :g | [ :x | f value: (g value: x) ] ]) > value: [:x | x + 1] > value: [:x | x - 1]) > value: 5 > > Butâ¦ It's a bit wordy. > > What I would like to be able to do (essentialy remove "value:"): > > (([ :f :g | [ :x | f (g x) ] ]) > [:x | x + 1] > [:x | x - 1]) > 5. > > Or in one line: > (([ :f :g | [ :x | f (g x) ] ]) [:x | x + 1] [:x | x - 1]) 5. > > While this might seem obscure, I would really find it useful. > > Can it be done? > > Thanks in advance > > > > -- > Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html >

Oct. 23, 2019