I am trying to understand how vector-set! is implemented. It looks to me like vector-set! is a special form - much like set! is. When I look at examples using vector-set! I see the following, desirable behavior (in guile).
(define test (lambda (v i) (vector-set! v i 0)))
(define v (make-vector 5 1))
v
$1 = #(1 1 1 1 1)
(test v 0)
v
$2 = #(0 1 1 1 1)
I can also do this (in guile)
(define test (lambda (v i) (vector-set! (eval v (interaction-environment)) i 0)))
(test (quote v) 3)
v
$21 = #(0 1 1 0 1)
Contrasting to the set! behavior:
(define a 1)
(define test2 (lambda b (begin (set! b 0) b)))
(test2 (quote a))
$26 = 0
a
$27 = 1
In this case, to my understanding the set! changes b to 0 (and not the 'evaluated" b (which should be a). The eval trick from above does not work here.
My question is: How is vector-set! implemented compared to set! (or set-variable-value!). Does vector-set! peak at it's first argument? Or something else? I have tried to look at some of scheme implementations but extracting the gist from the code is tricky. Perhaps someone has an explanation or a link to some (sicp style) scheme implementation.
The function vector-set! is a so-called primitive.
It is a function (not a special form), but it must be implemented within the runtime.
Note: A special form is a form that uses an evaluation order different from the order used in a normal application. Therefore if, cond, or and others are special forms.
Some implementations (I can't remember if Guile is one of them) has a function primitive? that can be used to test whether a function is a primitive or not.
> (primitive? vector-set!)
#t