Re: [Scheme-reports] Pattern matching and list comprehensions

In Scheme, any implementation of Scheme will get traction once it has
a minimum of RnRS-compatibility (and RnRS is a very short standard,
except for n=6) plus a module system plus a library repository, and
each Scheme implementation becomes its own little island, Any short,
succinct operator that arises on one island will not be understood on
another island. Hence the need in Scheme for fully specifying what
you mean in each name.

only

> ((append) is not needed here.)

Actually, it is:

(let ((x (list 1 2 3))
      (y (list 4 5 6)))
  (apply f (append x y)))
==
(f 1 2 3 4 5 6)

but:

(let ((x (list 1 2 3))
      (y (list 4 5 6)))
  (apply f x y))
==
(f (list 1 2 3) 4 5 6)

>
> It's not only that -- it is also relevant how arguments are applied to
> the predicate. To be honest, I have no intuition of whether such
> generalization is good. Can you come up with any real-world usage
> example? (Like: multiple argument map allows you to easily define the
> code that computes the dot product)
>
> Sorry, I don't have production examples right before my eyes now, so
> anything I come up with would be somewhat artificial.
> Let's say you have two function graphs in two buffers and want to compute
> their relation at all points where the denominator is not zero:
>
> (define nom-list)
> (define denom-list)
> (define ratio-list (call-with-values (lambda () (filter (lambda (a b) (not
> (zero? b))) nom-list denom-list)) (lambda (l1 l2) (map / l1 l2))))
>
> (I intentionally have not used any more procedures of prelude.scm in this
> example.)
>
>
> Pozdrawiam
> M.
>
>
>
> С уважением,
>
> denin@x
>
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>