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In scheme when defined
(define f (lambda (a b c d) d))
(define l (list 'a 'b 'c 'd))
Why it does not do argument destructuring? I mean arguments should evaluate first, why destructuring is not part of that?
(f . l)
What are reasons that this expression is not equal with following?
(apply f l)
The main reason is, (f . l) can only work if l is an identifier (or some other atomic literal), and not if it's a more complicated expression. Consider a function for calculating the sum-of-squares:
(define (sum-of-squares . nums)
(apply + (map square nums)))
Here, you cannot rewrite the (apply + (map square nums)) into (+ . (map square nums)), because that is equivalent (at read-time, way before evaluation happens) to (+ map square nums). And map, square, and nums are not numbers. ;-)
Therefore, implementations have to supply an apply procedure. And once you do, there's no real point to supporting a dotted procedure-application expression that only works some of the time, when apply works correctly all the time.
(Many thanks to Brian Mastenbrook for explaining this to me years ago, back when I had a similar question myself.)
