Pharo and special unary selectors
Hi, just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ... In the most simple case one can easily implement own units just by providing a unary messages: 1 m 1 second 1 px 1 EUR One can easily implement an own Money class with a currency and then do polymorphic tricks like 10 EUR + 20 EUR But we can currently can not implement special unary selectors (including special unary selectors with unicode) like: 100 % 20 $ 40 ⬠12 Ⱐ(for promille) Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind). Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment. Thx T.
From one perspective, full names are clearer at the cost of some typing
33 percent 45 dollar 100 kilometerPerHour 4 newtonMeter 200 bitsPerSecond And just like there is a limited namespace for class names (and prefixes to separate them), the namespace of selectors is global and limited too. #percent and #second(s) already exist, for example. So there might be conflicts.
On 17 Nov 2017, at 10:32, Torsten Bergmann <astares@gmx.de> wrote:
Hi,
just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ...
In the most simple case one can easily implement own units just by providing a unary messages:
1 m 1 second 1 px 1 EUR
One can easily implement an own Money class with a currency and then do polymorphic tricks like
10 EUR + 20 EUR
But we can currently can not implement special unary selectors (including special unary selectors with unicode) like:
100 % 20 $ 40 ⬠12 Ⱐ(for promille)
Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind).
Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment.
Thx T.
Well you would change the syntax of Pharo, which I don't think will be met with a lot of enthusiasm. How would you distinguish it from unary messages? How would you distinguish it from something that should trigger compilation error instead? ($ for characters) Also; 1 ml is one milliliter, or one mile? Also considering how was the #, selector was shut down for Bloc vectors, this seems rather bold. :) But I would imagine that people do and will do named unary selectors within their projects (which is something quite different to having all of it in Pharo by default) Peter On Fri, Nov 17, 2017 at 10:32 AM, Torsten Bergmann <astares@gmx.de> wrote:
Hi,
just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ...
In the most simple case one can easily implement own units just by providing a unary messages:
1 m 1 second 1 px 1 EUR
One can easily implement an own Money class with a currency and then do polymorphic tricks like
10 EUR + 20 EUR
But we can currently can not implement special unary selectors (including special unary selectors with unicode) like:
100 % 20 $ 40 ⬠12 Ⱐ(for promille)
Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind).
Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment.
Thx T.
Well you would change the syntax of Pharo
I'm not sure this is a syntax change like others. Haven yet thought about it too deeply. Where is the difference between an unary method #m and #% from the callers point of view? Either there is an argument object then % is a binary - if not it is an unary. Maybe it is hard to parse or introduces new problems.
But I would imagine that people do and will do named unary selectors within their projects (which is something quite different to having all of it in Pharo by default)
I dont want to have them inside by default in the base image - but people might be interested in implementing % (for percent), ⬠(Euro) or â° (promille) as own unary messages in an own custom external package. Or having binary messages with Unicode. Just an idea to discuss what it would mean to have such beasts or if it would be useful ;) Bye T. Â
I would really like to see % removed as a binary selector and available to use in unary or keyword ones. The only implementor in a Pharo 6 image is: % aNumber ^ self \\ aNumber So it's juts aliasing \\ , and % most widespread usage in the real world is por percentages (the use in modular arithmetic is more a programming thing that math notation I think). And for allowing more Unicode code points for selector names I'm totally in for Symbols, Arrows, Math Symbols, etc... We just need to analyse the ones that makes sense as binary selectors, and the ones allowed for unary and keyword ones. This will allow us to write pretty cool DSLs. Just my opinion. On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de> wrote:
Hi,
just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ...
In the most simple case one can easily implement own units just by providing a unary messages:
1 m 1 second 1 px 1 EUR
One can easily implement an own Money class with a currency and then do polymorphic tricks like
10 EUR + 20 EUR
But we can currently can not implement special unary selectors (including special unary selectors with unicode) like:
100 % 20 $ 40 ⬠12 Ⱐ(for promille)
Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind).
Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment.
Thx T.
2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli@gmail.com>:
I would really like to see % removed as a binary selector and available to use in unary or keyword ones. The only implementor in a Pharo 6 image is:
% aNumber
^ self \\ aNumber
+1, such alias has nothing to do in Kernel So it's juts aliasing \\ , and % most widespread usage in the real world is
por percentages (the use in modular arithmetic is more a programming thing that math notation I think).
And for allowing more Unicode code points for selector names I'm totally in for Symbols, Arrows, Math Symbols, etc... We just need to analyse the ones that makes sense as binary selectors, and the ones allowed for unary and keyword ones. This will allow us to write pretty cool DSLs.
Just my opinion.
This could also be the case for punctuation like ! and ?
The idea of Torsten is more generic, any combination of binary char could be used.
From what I understand from https://en.wikipedia.org/wiki/LR_parser we would just have to scan one more token ahead for deciding if unary or binary, and could preserve our simple shift reduce steps... So it seems doable for resolving the send. More problematic would be the declaration of method, if we have both a unary + and a binary +, we will need new syntax for marking the difference.
Whether it's worth or not is another matter... On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de> wrote:
Hi,
just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ...
In the most simple case one can easily implement own units just by providing a unary messages:
1 m 1 second 1 px 1 EUR
One can easily implement an own Money class with a currency and then do polymorphic tricks like
10 EUR + 20 EUR
But we can currently can not implement special unary selectors (including special unary selectors with unicode) like:
100 % 20 $ 40 ⬠12 Ⱐ(for promille)
Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind).
Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment.
Thx T.
Le 17/11/2017 à 10:14, Nicolas Cellier a écrit :
2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli@gmail.com <mailto:g.cotelli@gmail.com>>:
I would really like to see % removed as a binary selector and available to use in unary or keyword ones. The only implementor in a Pharo 6 image is:
 % aNumber
   ^ self \\ aNumber
+1, such alias has nothing to do in Kernel
So it's juts aliasing \\ , and % most widespread usage in the real world is por percentages (the use in modular arithmetic is more a programming thing that math notation I think).
And for allowing more Unicode code points for selector names I'm totally in for Symbols, Arrows, Math Symbols, etc... We just need to analyse the ones that makes sense as binary selectors, and the ones allowed for unary and keyword ones. This will allow us to write pretty cool DSLs.
Just my opinion.
This could also be the case for punctuation like ! and ?
The idea of Torsten is more generic, any combination of binary char could be used. From what I understand from https://en.wikipedia.org/wiki/LR_parser we would just have to scan one more token ahead for deciding if unary or binary, and could preserve our simple shift reduce steps...
The Smalltalk parsers being handwritten, there wouldn't be shift/reduces to contend with, and, anyway, the lexer doesn't shift/reduce; it would simply creates a token up to the next separator (that is goble up the next space/cr/end of line dot/closing parenthesis/etc...)
So it seems doable for resolving the send.
Sort of. The parser difficulty would be this one: anObject % print Is this a binary selector with a print argument or two unary selectors? Using the symbol table when you parse would solve it, but that is certainly not context free...
More problematic would be the declaration of method, if we have both a unary + and a binary +, we will need new syntax for marking the difference.
In most cases, distinguishing between unary + declaration and binary + declaration would be doable: + whatever is the start of a binary selector + ^ self is the start (or the declaration of) an unary selector. But writing + self Can be interpreted as either unary plus doing self, or binary + method definition...
Whether it's worth or not is another matter...
Well, one should probably try to implement the various parsers for that (extend RB, extend the SmaCC Smalltalk parser, extend the Petit Parser) to see how much complexity it would bring. Coming up with strange interpretations one could do with that syntax can be helpfull as well. Regards, Thierry
On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de <mailto:astares@gmx.de>> wrote:
Hi,
just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ...
In the most simple case one can easily implement own units just by providing a unary messages:
 1 m  1 second  1 px  1 EUR
One can easily implement an own Money class with a currency and then do polymorphic tricks like
 10 EUR + 20 EUR
But we can currently can not implement special unary selectors (including special unary selectors with unicode) like:
 100 %  20 $  40 ⬠ 12 â°Â (for promille)
Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind).
Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment.
Thx T.
Parsing difficulty also means that it is harder for humans to understand, to explain to (new) users. It would be pretty strange to have binary selectors that are unary, is my first reaction.
On 17 Nov 2017, at 18:32, Thierry Goubier <thierry.goubier@gmail.com> wrote:
Le 17/11/2017 à 10:14, Nicolas Cellier a écrit :
2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli@gmail.com <mailto:g.cotelli@gmail.com>>: I would really like to see % removed as a binary selector and available to use in unary or keyword ones. The only implementor in a Pharo 6 image is: % aNumber ^ self \\ aNumber +1, such alias has nothing to do in Kernel So it's juts aliasing \\ , and % most widespread usage in the real world is por percentages (the use in modular arithmetic is more a programming thing that math notation I think). And for allowing more Unicode code points for selector names I'm totally in for Symbols, Arrows, Math Symbols, etc... We just need to analyse the ones that makes sense as binary selectors, and the ones allowed for unary and keyword ones. This will allow us to write pretty cool DSLs. Just my opinion. This could also be the case for punctuation like ! and ? The idea of Torsten is more generic, any combination of binary char could be used. From what I understand from https://en.wikipedia.org/wiki/LR_parser we would just have to scan one more token ahead for deciding if unary or binary, and could preserve our simple shift reduce steps...
The Smalltalk parsers being handwritten, there wouldn't be shift/reduces to contend with, and, anyway, the lexer doesn't shift/reduce; it would simply creates a token up to the next separator (that is goble up the next space/cr/end of line dot/closing parenthesis/etc...)
So it seems doable for resolving the send.
Sort of. The parser difficulty would be this one:
anObject % print
Is this a binary selector with a print argument or two unary selectors?
Using the symbol table when you parse would solve it, but that is certainly not context free...
More problematic would be the declaration of method, if we have both a unary + and a binary +, we will need new syntax for marking the difference.
In most cases, distinguishing between unary + declaration and binary + declaration would be doable:
+ whatever
is the start of a binary selector
+ ^ self
is the start (or the declaration of) an unary selector.
But writing
+ self
Can be interpreted as either unary plus doing self, or binary + method definition...
Whether it's worth or not is another matter...
Well, one should probably try to implement the various parsers for that (extend RB, extend the SmaCC Smalltalk parser, extend the Petit Parser) to see how much complexity it would bring.
Coming up with strange interpretations one could do with that syntax can be helpfull as well.
Regards,
Thierry
On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de <mailto:astares@gmx.de>> wrote: Hi, just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ... In the most simple case one can easily implement own units just by providing a unary messages: 1 m 1 second 1 px 1 EUR One can easily implement an own Money class with a currency and then do polymorphic tricks like 10 EUR + 20 EUR But we can currently can not implement special unary selectors (including special unary selectors with unicode) like: 100 % 20 $ 40 ⬠12 Ⱐ(for promille) Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind). Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment. Thx T.
Le 17/11/2017 à 11:08, Sven Van Caekenberghe a écrit :
Parsing difficulty also means that it is harder for humans to understand, to explain to (new) users.
Agreed. This is a significant issue in some programming languages.
It would be pretty strange to have binary selectors that are unary, is my first reaction.
Or that it could be both... An unary +, then a binary +, maybe not in the same class... Thierry
On 17 Nov 2017, at 18:32, Thierry Goubier <thierry.goubier@gmail.com> wrote:
Le 17/11/2017 à 10:14, Nicolas Cellier a écrit :
2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli@gmail.com <mailto:g.cotelli@gmail.com>>: I would really like to see % removed as a binary selector and available to use in unary or keyword ones. The only implementor in a Pharo 6 image is: % aNumber ^ self \\ aNumber +1, such alias has nothing to do in Kernel So it's juts aliasing \\ , and % most widespread usage in the real world is por percentages (the use in modular arithmetic is more a programming thing that math notation I think). And for allowing more Unicode code points for selector names I'm totally in for Symbols, Arrows, Math Symbols, etc... We just need to analyse the ones that makes sense as binary selectors, and the ones allowed for unary and keyword ones. This will allow us to write pretty cool DSLs. Just my opinion. This could also be the case for punctuation like ! and ? The idea of Torsten is more generic, any combination of binary char could be used. From what I understand from https://en.wikipedia.org/wiki/LR_parser we would just have to scan one more token ahead for deciding if unary or binary, and could preserve our simple shift reduce steps...
The Smalltalk parsers being handwritten, there wouldn't be shift/reduces to contend with, and, anyway, the lexer doesn't shift/reduce; it would simply creates a token up to the next separator (that is goble up the next space/cr/end of line dot/closing parenthesis/etc...)
So it seems doable for resolving the send.
Sort of. The parser difficulty would be this one:
anObject % print
Is this a binary selector with a print argument or two unary selectors?
Using the symbol table when you parse would solve it, but that is certainly not context free...
More problematic would be the declaration of method, if we have both a unary + and a binary +, we will need new syntax for marking the difference.
In most cases, distinguishing between unary + declaration and binary + declaration would be doable:
+ whatever
is the start of a binary selector
+ ^ self
is the start (or the declaration of) an unary selector.
But writing
+ self
Can be interpreted as either unary plus doing self, or binary + method definition...
Whether it's worth or not is another matter...
Well, one should probably try to implement the various parsers for that (extend RB, extend the SmaCC Smalltalk parser, extend the Petit Parser) to see how much complexity it would bring.
Coming up with strange interpretations one could do with that syntax can be helpfull as well.
Regards,
Thierry
On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de <mailto:astares@gmx.de>> wrote: Hi, just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ... In the most simple case one can easily implement own units just by providing a unary messages: 1 m 1 second 1 px 1 EUR One can easily implement an own Money class with a currency and then do polymorphic tricks like 10 EUR + 20 EUR But we can currently can not implement special unary selectors (including special unary selectors with unicode) like: 100 % 20 $ 40 ⬠12 Ⱐ(for promille) Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind). Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment. Thx T.
2017-11-17 18:32 GMT+01:00 Thierry Goubier <thierry.goubier@gmail.com>:
Le 17/11/2017 à 10:14, Nicolas Cellier a écrit :
2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli@gmail.com <mailto: g.cotelli@gmail.com>>:
I would really like to see % removed as a binary selector and available to use in unary or keyword ones. The only implementor in a Pharo 6 image is:
% aNumber
^ self \\ aNumber
+1, such alias has nothing to do in Kernel
So it's juts aliasing \\ , and % most widespread usage in the real world is por percentages (the use in modular arithmetic is more a programming thing that math notation I think).
And for allowing more Unicode code points for selector names I'm totally in for Symbols, Arrows, Math Symbols, etc... We just need to analyse the ones that makes sense as binary selectors, and the ones allowed for unary and keyword ones. This will allow us to write pretty cool DSLs.
Just my opinion.
This could also be the case for punctuation like ! and ?
The idea of Torsten is more generic, any combination of binary char could be used. From what I understand from https://en.wikipedia.org/wiki/LR_parser we would just have to scan one more token ahead for deciding if unary or binary, and could preserve our simple shift reduce steps...
The Smalltalk parsers being handwritten, there wouldn't be shift/reduces to contend with, and, anyway, the lexer doesn't shift/reduce; it would simply creates a token up to the next separator (that is goble up the next space/cr/end of line dot/closing parenthesis/etc...)
I don't have academical cursus, so I may be approximate, but the manually written parsers just have to read a single token ahead so far, and linearly build the parseNode, to me it was equivalent.
So it seems doable for resolving the send.
Sort of. The parser difficulty would be this one:
anObject % print
Yes, that's a severe limitation. Context free => it's a binary... Or we have to use ( ). But then it's unfriendly to have different rules for unary symbols versus unary words... It devaluates the idea...
Is this a binary selector with a print argument or two unary selectors?
Using the symbol table when you parse would solve it, but that is certainly not context free...
More problematic would be the declaration of method, if we have both a
unary + and a binary +, we will need new syntax for marking the difference.
In most cases, distinguishing between unary + declaration and binary + declaration would be doable:
+ whatever
is the start of a binary selector
+ ^ self
is the start (or the declaration of) an unary selector.
But writing
+ self
Can be interpreted as either unary plus doing self, or binary + method definition...
Yes I was thinking of similar issues... + b | c | a binary plus with unused temp and implicit ^self, or unary + with binary | sent to b with unary (c |) parameter etc... So we need a new syntax meaning that there is no parameter, like + ][ or anything yet unused...
Whether it's worth or not is another matter...
Well, one should probably try to implement the various parsers for that (extend RB, extend the SmaCC Smalltalk parser, extend the Petit Parser) to see how much complexity it would bring.
Coming up with strange interpretations one could do with that syntax can be helpfull as well.
Regards,
Thierry
On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de
<mailto:astares@gmx.de>> wrote:
Hi,
just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ...
In the most simple case one can easily implement own units just by providing a unary messages:
1 m 1 second 1 px 1 EUR
One can easily implement an own Money class with a currency and then do polymorphic tricks like
10 EUR + 20 EUR
But we can currently can not implement special unary selectors (including special unary selectors with unicode) like:
100 % 20 $ 40 ⬠12 Ⱐ(for promille)
Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind).
Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment.
Thx T.
If a valid Smalltalk method identifier contains only... [a-zA-Z][a-zA-Z0-9]* http://www.osdata.com/programming/firstprograms/valididentifiers.html then one option could be that unary symbols must touch the previous identifier, i.e. no intervening whitespace, 100% 20$ 40⬠12Ⱐportion% someMoney$ or pick a new "unary separator/binder" 100'% or 100 '% 20'$ or 20 '$ 40'⬠or 40 '⬠12'Ⱐor 12 'Ⱐportion'% someMoney'$ or re-use the existing colon which indicates an argument to the right, to indicate an argument to the left.... 100 :% 20 :$ 40 :⬠12 :Ⱐ(for promille) portion :% someMoney :$ which is unambiguous regarding block variable definitions since no messages are valid in the block variable definition area, but this may complicate precedence semantics due to its similarity to a keyword selector, and would complicate things if the space was missing. On 18 November 2017 at 04:02, Nicolas Cellier < nicolas.cellier.aka.nice@gmail.com> wrote:
2017-11-17 18:32 GMT+01:00 Thierry Goubier <thierry.goubier@gmail.com>:
Le 17/11/2017 à 10:14, Nicolas Cellier a écrit :
2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli@gmail.com <mailto: g.cotelli@gmail.com>>:
I would really like to see % removed as a binary selector and available to use in unary or keyword ones. The only implementor in a Pharo 6 image is:
% aNumber
^ self \\ aNumber
+1, such alias has nothing to do in Kernel
So it's juts aliasing \\ , and % most widespread usage in the real world is por percentages (the use in modular arithmetic is more a programming thing that math notation I think).
And for allowing more Unicode code points for selector names I'm totally in for Symbols, Arrows, Math Symbols, etc... We just need to analyse the ones that makes sense as binary selectors, and the ones allowed for unary and keyword ones. This will allow us to write pretty cool DSLs.
Just my opinion.
This could also be the case for punctuation like ! and ?
The idea of Torsten is more generic, any combination of binary char could be used. From what I understand from https://en.wikipedia.org/wiki/LR_parser we would just have to scan one more token ahead for deciding if unary or binary, and could preserve our simple shift reduce steps...
The Smalltalk parsers being handwritten, there wouldn't be shift/reduces to contend with, and, anyway, the lexer doesn't shift/reduce; it would simply creates a token up to the next separator (that is goble up the next space/cr/end of line dot/closing parenthesis/etc...)
I don't have academical cursus, so I may be approximate, but the manually written parsers just have to read a single token ahead so far, and linearly build the parseNode, to me it was equivalent.
So it seems doable for resolving the send.
Sort of. The parser difficulty would be this one:
anObject % print
Yes, that's a severe limitation. Context free => it's a binary... Or we
have to use ( ). But then it's unfriendly to have different rules for unary symbols versus unary words... It devaluates the idea...
Is this a binary selector with a print argument or two unary selectors?
Less ambiguous... anObject'% print anObject '% print
Using the symbol table when you parse would solve it, but that is certainly not context free...
More problematic would be the declaration of method, if we have both a
unary + and a binary +, we will need new syntax for marking the difference.
In most cases, distinguishing between unary + declaration and binary + declaration would be doable:
+ whatever
is the start of a binary selector
+ ^ self
is the start (or the declaration of) an unary selector.
But writing
+ self
Can be interpreted as either unary plus doing self, or binary + method definition...
a "unary binder" could distinguish them... binary method definition... + self unary method definition... '+ self
issues...
+ b | c |
a binary plus with unused temp and implicit ^self, or unary + with binary | sent to b with unary (c |) parameter etc...
+ b | c | binary plus, unused temporary c '+ b | c | unary plus, first | is binary, second | is unary or maybe it would need to be... '+ b | c'|
So we need a new syntax meaning that there is no parameter, like + ][ or anything yet unused...
without ' + || b | c | empty local variable definition, next | is binary, second | is unary also with local variable... + | lv1 | b | c | + | lv1 | b | c'|
Whether it's worth or not is another matter...
Well, one should probably try to implement the various parsers for that (extend RB, extend the SmaCC Smalltalk parser, extend the Petit Parser) to see how much complexity it would bring.
Coming up with strange interpretations one could do with that syntax can be helpfull as well.
Regards,
Thierry
On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de
<mailto:astares@gmx.de>> wrote:
Hi,
just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ...
In the most simple case one can easily implement own units just by providing a unary messages:
1 m 1 second 1 px 1 EUR
One can easily implement an own Money class with a currency and then do polymorphic tricks like
10 EUR + 20 EUR
btw, did the recently announced QA Release Tests add enforcement all selectors to start with a lowercase? I felt that one a bit overly-restrictive, which would break such a currency DSL. cheers -ben
But we can currently can not implement special unary selectors (including special unary selectors with unicode) like:
100 % 20 $ 40 ⬠12 Ⱐ(for promille)
Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind).
Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment.
Thx T.
Personnally, I against adding those special symbols. They add close to nothing (except complexity in the parser) to what we can actually do! Besides, what does 30$ + 17$ add up to? Oh! Did I tell you it was actually $30USD + $17CAN ? :) ----------------- Benoît St-Jean Yahoo! Messenger: bstjean Twitter: @BenLeChialeux Pinterest: benoitstjean Instagram: Chef_Benito IRC: lamneth Blogue: endormitoire.wordpress.com "A standpoint is an intellectual horizon of radius zero". (A. Einstein) On Friday, November 17, 2017, 6:41:11 PM EST, Ben Coman <btc@openinworld.com> wrote: If a valid Smalltalk method identifier contains only... [a-zA-Z][a-zA-Z0-9]*http://www.osdata.com/programming/firstprograms/valididentifiers.html then one option could be that unary symbols must touch the previous identifier, i.e. no intervening whitespace,  100%   20$  40⬠ 12â°Â  portion% someMoney$ or pick a new "unary separator/binder"  100'%  or 100 '%  20'$    or  20 '$  40'â¬Â    or 40 '⬠ 12'â°Â   or 12 'â°Â  portion'% someMoney'$ or re-use the existing colon which indicates an argument to the right, to indicate an argument to the left....  100 :%   20 :$  40 :⬠ 12 :â°Â (for promille) portion :% someMoney :$ which is unambiguous regarding block variable definitions since no messages are valid in the block variable definition area,but this may complicate precedence semantics due to its similarity to a keyword selector, and would complicate things if the space was missing. On 18 November 2017 at 04:02, Nicolas Cellier <nicolas.cellier.aka.nice@gmail.com> wrote: 2017-11-17 18:32 GMT+01:00 Thierry Goubier <thierry.goubier@gmail.com>: Le 17/11/2017 à 10:14, Nicolas Cellier a écrit : 2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli@gmail.com <mailto:g.cotelli@gmail.com>>:   I would really like to see % removed as a binary selector and   available to use in unary or keyword ones. The only implementor in a   Pharo 6 image is:     % aNumber       ^ self \\ aNumber +1, such alias has nothing to do in Kernel   So it's juts aliasing \\ , and % most widespread usage in the real   world is por percentages (the use in modular arithmetic is more a   programming thing that math notation I think).   And for allowing more Unicode code points for selector names I'm   totally in for Symbols, Arrows, Math Symbols, etc... We just need to   analyse the ones that makes sense as binary selectors, and the ones   allowed for unary and keyword ones. This will allow us to write   pretty cool DSLs.   Just my opinion. This could also be the case for punctuation like ! and ? The idea of Torsten is more generic, any combination of binary char could be used.  From what I understand from https://en.wikipedia.org/wiki/ LR_parser we would just have to scan one more token ahead for deciding if unary or binary, and could preserve our simple shift reduce steps... The Smalltalk parsers being handwritten, there wouldn't be shift/reduces to contend with, and, anyway, the lexer doesn't shift/reduce; it would simply creates a token up to the next separator (that is goble up the next space/cr/end of line dot/closing parenthesis/etc...) I don't have academical cursus, so I may be approximate, but the manually written parsers just have to read a single token ahead so far, and linearly build the parseNode, to me it was equivalent. So it seems doable for resolving the send. Sort of. The parser difficulty would be this one: anObject % print Yes, that's a severe limitation. Context free => it's a binary... Or we have to use ( ). But then it's unfriendly to have different rules for unary symbols versus unary words...It devaluates the idea... Is this a binary selector with a print argument or two unary selectors? Less ambiguous...anObject'% printanObject '% print  Using the symbol table when you parse would solve it, but that is certainly not context free... More problematic would be the declaration of method, if we have both a unary + and a binary +, we will need new syntax for marking the difference. In most cases, distinguishing between unary + declaration and binary + declaration would be doable: + whatever is the start of a binary selector + ^ self is the start (or the declaration of) an unary selector. But writing + self Can be interpreted as either unary plus doing self, or binary + method definition... a "unary binder" could distinguish them... binary method definition... + self unary method definition...'+ self    issues... + b | c | a binary plus with unused temp and implicit ^self, or unary + with binary | sent to b with unary (c |) parameter etc... + b | c | binary plus, unused temporary c '+ b | c |unary plus, first | is binary, second | is unary  or maybe it would need to be...  '+ b | c'|  So we need a new syntax meaning that there is no parameter, like + ][ or anything yet unused... without ' + || b | c |empty local variable definition, next | is binary, second | is unary  also with local variable...+ | lv1 | b | c | + | lv1 | b | c'|  Whether it's worth or not is another matter... Well, one should probably try to implement the various parsers for that (extend RB, extend the SmaCC Smalltalk parser, extend the Petit Parser) to see how much complexity it would bring. Coming up with strange interpretations one could do with that syntax can be helpfull as well. Regards, Thierry   On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de   <mailto:astares@gmx.de>> wrote:     Hi,     just something to think about: one thing I always liked about     Smalltalk is that it allows for nice DSL's. We have nice things     like a unit framework in Pharo, ...     In the most simple case one can easily implement own units just     by providing a unary messages:       1 m       1 second       1 px       1 EUR     One can easily implement an own Money class with a currency and     then do polymorphic tricks like       10 EUR + 20 EUR btw, did the recently announced QA Release Tests add enforcement all selectors to start with a lowercase?I felt that one a bit overly-restrictive, which would break such a currency DSL. cheers -ben     But we can currently can not implement special unary selectors     (including special unary selectors with unicode) like:       100 %       20 $       40 ⬠      12 â°Â (for promille)     Especially things like 20 % would be nice for layout issues or     other (Bloc comes to mind).     Maybe we should put that on the roadmap of Pharo because IMHO it     would be cool to support such things in the     future. Dont know how much effort it currently means on the     technical level but maybe others can comment.     Thx     T.
Le 17 nov. 2017 1:03 PM, "Nicolas Cellier" < nicolas.cellier.aka.nice@gmail.com> a écrit : 2017-11-17 18:32 GMT+01:00 Thierry Goubier <thierry.goubier@gmail.com>:
Le 17/11/2017 à 10:14, Nicolas Cellier a écrit :
2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli@gmail.com <mailto: g.cotelli@gmail.com>>:
I would really like to see % removed as a binary selector and available to use in unary or keyword ones. The only implementor in a Pharo 6 image is:
% aNumber
^ self \\ aNumber
+1, such alias has nothing to do in Kernel
So it's juts aliasing \\ , and % most widespread usage in the real world is por percentages (the use in modular arithmetic is more a programming thing that math notation I think).
And for allowing more Unicode code points for selector names I'm totally in for Symbols, Arrows, Math Symbols, etc... We just need to analyse the ones that makes sense as binary selectors, and the ones allowed for unary and keyword ones. This will allow us to write pretty cool DSLs.
Just my opinion.
This could also be the case for punctuation like ! and ?
The idea of Torsten is more generic, any combination of binary char could be used. From what I understand from https://en.wikipedia.org/wiki/LR_parser we would just have to scan one more token ahead for deciding if unary or binary, and could preserve our simple shift reduce steps...
The Smalltalk parsers being handwritten, there wouldn't be shift/reduces to contend with, and, anyway, the lexer doesn't shift/reduce; it would simply creates a token up to the next separator (that is goble up the next space/cr/end of line dot/closing parenthesis/etc...)
I don't have academical cursus, so I may be approximate, but the manually written parsers just have to read a single token ahead so far, and linearly build the parseNode, to me it was equivalent. What I meant is that at the tokenifier stage, the parser already combines characters into a single token. So the parser is yes using only a single token lookahead,, but where a token can be multiple characters.
So it seems doable for resolving the send.
Sort of. The parser difficulty would be this one:
anObject % print
Yes, that's a severe limitation. Context free => it's a binary... Or we have to use ( ). But then it's unfriendly to have different rules for unary symbols versus unary words... It devaluates the idea... I agree.
Is this a binary selector with a print argument or two unary selectors?
Using the symbol table when you parse would solve it, but that is certainly not context free...
More problematic would be the declaration of method, if we have both a
unary + and a binary +, we will need new syntax for marking the difference.
In most cases, distinguishing between unary + declaration and binary + declaration would be doable:
+ whatever
is the start of a binary selector
+ ^ self
is the start (or the declaration of) an unary selector.
But writing
+ self
Can be interpreted as either unary plus doing self, or binary + method definition...
Yes I was thinking of similar issues... + b | c | a binary plus with unused temp and implicit ^self, or unary + with binary | sent to b with unary (c |) parameter etc... I haven't seen this one coming. So we need a new syntax meaning that there is no parameter, like + ][ or anything yet unused... It starts to look very convoluted. Yuck. Thierry
Whether it's worth or not is another matter...
Well, one should probably try to implement the various parsers for that (extend RB, extend the SmaCC Smalltalk parser, extend the Petit Parser) to see how much complexity it would bring.
Coming up with strange interpretations one could do with that syntax can be helpfull as well.
Regards,
Thierry
On Fri, Nov 17, 2017 at 6:32 AM, Torsten Bergmann <astares@gmx.de
<mailto:astares@gmx.de>> wrote:
Hi,
just something to think about: one thing I always liked about Smalltalk is that it allows for nice DSL's. We have nice things like a unit framework in Pharo, ...
In the most simple case one can easily implement own units just by providing a unary messages:
1 m 1 second 1 px 1 EUR
One can easily implement an own Money class with a currency and then do polymorphic tricks like
10 EUR + 20 EUR
But we can currently can not implement special unary selectors (including special unary selectors with unicode) like:
100 % 20 $ 40 ⬠12 Ⱐ(for promille)
Especially things like 20 % would be nice for layout issues or other (Bloc comes to mind).
Maybe we should put that on the roadmap of Pharo because IMHO it would be cool to support such things in the future. Dont know how much effort it currently means on the technical level but maybe others can comment.
Thx T.
participants (8)
-
Ben Coman -
Benoit St-Jean -
Gabriel Cotelli -
Nicolas Cellier -
Peter Uhnák -
Sven Van Caekenberghe -
Thierry Goubier -
Torsten Bergmann