A procedure with setter is a special kind of procedure which normally behaves like any accessor procedure, that is a procedure which accesses a data structure. The difference is that this kind of procedure has a so-called setter attached, which is a procedure for storing something into a data structure.
Procedures with setters are treated specially when the procedure appears
in the special form
set!. How it works is best shown by example.
Suppose we have a procedure called
foo-ref, which accepts two
arguments, a value of type
foo and an integer. The procedure
returns the value stored at the given index in the
f be a variable containing such a
(foo-ref f 0) ⇒ bar (foo-ref f 1) ⇒ braz
Also suppose that a corresponding setter procedure called
foo-set! does exist.
(foo-set! f 0 'bla) (foo-ref f 0) ⇒ bla
Now we could create a new procedure called
foo, which is a
procedure with setter, by calling
the accessor and setter procedures
Let us call this new procedure
(define foo (make-procedure-with-setter foo-ref foo-set!))
foo can from now on be used to either read from the data
structure stored in
f, or to write into the structure.
(set! (foo f 0) 'dum) (foo f 0) ⇒ dum
Create a new procedure which behaves like procedure, but with the associated setter setter.
#t if obj is a procedure with an
associated setter procedure.
Return the procedure of proc, which must be an applicable struct.
Return the setter of proc, which must be either a procedure with setter or an operator struct.
Working definitions would be:
(define foo-ref vector-ref) (define foo-set! vector-set!) (define f (make-vector 2 #f))