[Impromptu] vector behavour

[David Smith]

Hi all,
Here is an interesting bit of information Impromptu users may find
usefull:

Persistance while using vectors works a bit differently.
Normally, the let instantiates a new local variable for each call.

(define countvar
(lambda (val)
(let ((v 1))
(+ val v)
)))
(countvar 3) -> 4, every time


If the variable is a vector, successive calls perform successive
operations on the variable instansiated by let when the function is
defined.

(define inccvctr
(lambda (vc)
(let ( (v #(1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0)))
(math:vector-rotate v (- 0 vc))
(print v) )))

(inccvctr 1)->

#(0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0)
#(0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0)
#(0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0)
#(0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0)
#(0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0)
#(0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0)

cheers,
Dave

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