On 7/19/12, David A. Wheeler <dwhee...@dwheeler.com> wrote:
> Alan Manuel Gloria:
>
>> Just when it's less than 2 weeks to spec freeze....
>
> :-).
>
>> I once had to code this expression:
>>
>> force(car(force(unwrap-box(s))))
>>
>> And it's ugly.
>>
>> I could use I-expressions:
>>
>> force
>> . car
>> . . force
>> . . . unwrap-box s
>>
>> But that wastes precious vertical space.
>>
>> So I propose the SUBLIST semantic.
>
> Hmm. Function composition isn't unknown, of course, but I'm skeptical about
> how often this kind of construct occurs. Every new rule has a mental cost;
> we need to make sure the cases are so common (or so egregious) that the
> construct is worth it. Otherwise, people will reject it as being "too
> complicated" to learn. The wrapped example you show above is actually how
> many other languages *would* show it.
>
> I also worry about using up one-character symbols; if we do anything like
> this, perhaps a multi-char symbol would do? We could also pick a few
> symbols to "reserve" for cases like this; again, it's not so bad if we
> reserve multi-character symbols.
Well, we could define an o-function that does composition:
define o
case-lambda
(f) f
(f g)
lambda parms
f apply(g parms)
(f g . rest)
{{f o g} o apply(o rest)}
Then: {force o car o force o unwrap-box}(s)
(or use <*> or <.> or something less egregious than o, now that I look
at it, o looks ugly, eh?)
Of course, the lack of true currying means that a slight variant like:
foo(bar(nitz quux(meow)))
Can't use a compose chain like o above.
foo $ bar nitz $ quux meow
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