[gambit-list] define-type with constraints
feeley at iro.umontreal.ca
Thu May 21 23:26:00 EDT 2009
On 21-May-09, at 3:22 PM, lowly coder wrote:
> I realize the purpose of define-type is to create structs, but I
> have struct with some constarints that must be satisfied, like in
> I want two vars, 'x' and 'twice-x', where twice-x = (* 2 x)
> In my code, I have created good-x-set! and good-twice-x-set!
> However, how do I overwrite the existing linked-x-set! and linked-
> twice-x-set! with my good-x-set! and good-twice-x-set! ?
Give private names for the actual setters, and define linked-x-set!
and linked-twice-x-set! so
that they call the private setter procedures.
(x linked-x $linked-x-set!)
(twice-x linked-twice-x $linked-twice-x-set!))
(define (linked-x-set! v x)
($linked-x-set! v x)
($linked-twice-x-set! v (* x 2)))
(define (linked-twice-x-set! v x)
($linked-x-set! v (/ x 2))
($linked-twice-x-set! v x))
(define obj (make-linked 0 0))
(linked-x-set! obj 11)
(linked-twice-x-set! obj 100)
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