[Impromptu] vector behavour

[Bruno Deferrari]

What happens if you build the vector dynamically?

Using '(vector 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0)' instead of '#(1 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0)'.

2009/3/20 David Smith <smithd at mail.com>:
> 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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