When the Maxima evaluator encounters f(x), it first checks whether f
has a function-value. If so, it uses that function-value. If not, it
evaluates f as a symbol, and tries to use *that* value as a function.
So:
f: x+1$
f(t)
tries to apply (x+1) to the argument t; but (x+1) is not a function.
The purpose of this evaluation is to support things like
foo(f,x):= f(x-1)$
foo(sqrt,y^2) => sqrt(y^2-1)
Personally, I'd prefer to make that syntactically different, e.g.
(f)(x-1) (which also works), but....
-s
On 1/10/07, Daniel Lakeland <dlakelan at street-artists.org> wrote:
> I know there's something I don't understand about maxima
> evaluation... I have an expression "fma_steady" and I want to create a
> function which has 2 parameters which returns the result of
> substituting those parameters into the expression fma_steady.
>
> Residfma(h,v) := block([expr:subst(v,vx(x), subst(h,h(x),lhs(fma_steady)))],
> ev(expr,diff));
>
> Here's what happens when I call it with an example set of arguments:
>
> (%i54) Residfma(1+a*x,1+b*x);
>
> h evaluates to a*x+1
> Improper name or value in functional position.
> #0: Residfma(h=a*x+1,v=b*x+1)
> -- an error. Quitting. To debug this try debugmode(true);
>
> what's going on?
>
>
> --
> Daniel Lakeland
> dlakelan at street-artists.org
> http://www.street-artists.org/~dlakelan
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