On Mon, 28 Sep 2009, Robert Dodier wrote:
< On Mon, Sep 28, 2009 at 3:17 PM, Edwin Woollett <woollett at charter.net> wrote:
<
< > (%i2) def4vec (a, a0, a1, a2, a3) := block (
< > ? ? ? ? ? ? ? a[0] : a0,
< > ? ? ? ? ? ? ? a[1] : a1,
< > ? ? ? ? ? ? ? a[2] : a2,
< > ? ? ? ? ? ? ? a[3] : a3 )$
<
< I guess this a job for the undocumented function arraysetapply,
< which evaluates the name of the array (as a[0] : ... does not).
<
< Try this:
<
< def4vec (a, a0, a1, a2, a3) :=
< (arraysetapply (a, [0], a0),
< arraysetapply (a, [1], a1),
< arraysetapply (a, [2], a2),
< arraysetapply (a, [3], a3));
<
< Does that have the intended effect?
<
< Maxima is more than a little bit confused about whether or
< not to evaluate the name of a function or array; sometimes
< it does and sometimes not.
There is a more general question here, too: how to write functions that
modify their arguments. I do this by writing a macro:
(%i49) def2vec(a,a0,a1)::=buildq([a:a,a0:a0,a1:a1],(a[0]:a0,a[1]:a1,a))$
(%i50) c : make_array(flonum,2);
(%o50) ?\#\(0\.0\ 0\.0\)
(%i51) def2vec(c,4,5);
(%o51) ?\#\(4\ 5\)
(%i52) c;
(%o52) ?\#\(4\ 5\)
Leo
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