Re: Shorter lambda expressions

[Panicz Maciej Godek <godek.maciek@gmail.com>]

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2016-09-23 18:44 GMT+02:00 Panicz Maciej Godek <godek.maciek@gmail.com>:

> I hope you don't mind me having dug this thread up, with an idea that is
> only loosely related with the original one.
>
> Recently I've been doing a small project in Clojure, and I've found that
> it provides a function called "partial" that performs a sort of partial
> application.
>
> With guile's curried definitions, it can be defined as
>
> (define ((partial function . args) . args+)
>   (apply function `(,@args ,@args+)))
>
> and it works rather nicely:
>
> (map (partial cons 2) '((3 4) (3 5) (4 6) (7 1)))
> ===> ((2 3 4) (2 3 5) (2 4 6) (2 7 1))
>
> I believe that -- since it is just a function -- it is much less
> controversial than both the short macros and SRFI-26  (although its range
> of applicability is narrower), and it seems to compose well with the spirit
> of Scheme, so maybe that would be a nice-have?
>

I take it back.
It is a terrible idea. Using explicit lambda is a better solution, because
it gives an opportunity to provide a name for an element of a list. Yet the
name "partial" reads terribly. Compound usages such as

(partial map (partial cons 1))

are much worse than their regular counterparts, i.e.

(lambda (list)
  (map (lambda (element)
             (cons 1 element))
          list))

because even though the latter are more lengthy, this length actually
serves the purpose of exposing the structure of expression. In the former
case, it isn't clear (without knowing the arity of map) what will be the
arity of the whole expression, nor the role of those arguments. It seems to
be a problem even in the case of well-known functions such as cons or map.

Sorry for the noise

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