[Pharo-dev] Pharo and special unary selectors

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Fri Nov 17 12:14:53 EST 2017

2017-11-17 17:40 GMT+01:00 Gabriel Cotelli <g.cotelli at 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 at 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 ‰  (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.
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