[Cuis-dev] extending the syntax for blocks and methods

[stephen at heaveneverywhere.com]

I did a hack a while back in VisualWorks (overriding messageNotUnderstood:) so that blocks would understand any messages sent to them as variations of value:value:. 
If you parse the message that’s not understood, get the number of arguments, and then send the right version of value:value: with the arguments, you can create a block with any number of arguments and use it with any calling method, as in,

	| summer sum |
	summer := [ :a :b | a + b].
	sum := summer add: 1 to: 2.


stp


--

                    Stephen Travis Pope   Ojai, California, USA    
          http://HeavenEverywhere.com <http://heaveneverywhere.com/>        http://FASTLabInc.com <http://fastlabinc.com/>
                       https://vimeo.com/user19434036/videos <https://vimeo.com/user19434036/videos>      http://heaveneverywhere.com/Reflections

--




> On Jul 16, 2022, at 2:51 AM, Luciano Notarfrancesco via Cuis-dev <cuis-dev at lists.cuis.st> wrote:
> 
> Hola!
> Interesting. Actually methods written like this look more complicated than the original Smalltalk-80 syntax to me, but it’s an interesting idea, maybe looks complicated just because I’m not used to it. Let us know how it goes.
> 
> Note that in Cuis #: is a valid binary message. I use it, maybe I’m the only one who uses it.
> 
> Another idea we discussed before was to compile ‘f(x)’ as ‘f value: x’. Note that this is not ambiguous with Smalltalk-80. We could also compile ‘a[i]’ as ‘a at: i’. I’m not sure if it’s worth to complicate the Smalltalk-80 syntax with things like this, tho, I also value simplicity.
> 
> 
> On Sat, 16 Jul 2022 at 01:39 Francisco Garau via Cuis-dev <cuis-dev at lists.cuis.st <mailto:cuis-dev at lists.cuis.st>> wrote:
> Hola Amigos -- just wanted to share with you some ideas I've been thinking about for a while. 
> 
> It all started when someone mentioned the colon in the syntax for block arguments could have whitespace around the argument so that you could write  [ : n | n + 1] 
> 
> It makes perfect sense to see the block as an "inlined" method that doesn't require any method-lookup; therefore, the selector is superfluous. But if we accepted the selector inside the block, it could be used as the variable holding the block. So, instead of writing succ := [:n | n + 1]  we could write  [succ: n | n + 1]  
> 
> Even better if the block evaluation accepts #: as a valid selector.  So you could write (succ: 3) = 4 instead of (succ value: 3) = 4. 
> 
> A short example will make this clear. 
> 
> Vanilla Smalltalk
> succ := [:n | n + 1].
> (succ value: 3) = 4. 
> 
> Extended Block Syntax
> [succ: n | n + 1]. 
> (succ: 3 ) = 4. 
> "the above is equivalent to" 
> (succ perform: #: with: 3) = 4. 
> 
> Being able to parse blocks with these syntax paves the way to unify the syntax for method definition—for example, a few hypothetical methods from the Point class. 
> 
> "Point class>x:y:" 
> [x: xInteger y: yInteger | 
>    ^self basicNew setX: xInteger setY: yInteger].
> 
> "Point>>abs"
> [abs | 
>    ^x abs @ y abs]. 
> 
> "Point>>extent:" 
> [extent: aPoint |
>    ^Rectangle origin: self extent: aPoint] 
> 
> Of course, it gets trickier when blocks have more than one argument.. 
> 
> [add: a to: b | a + b]. 
> (add_to value: 3 value: 4) = 7. "old style block evaluation" 
> (add: 3 to: 4) = 7. 
> 
> I think building a separate Parser is a sensible approach -- is there a Smalltalk Parser as a separate package that can be tweaked without affecting the running image?
> 
> Thanks,
> Francisco
> 
> 
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