Re: Mupad: Plot problem "Can't evaluate to boolean"

Marten wrote:

d_f:=(f,k,g)->(if d_h(f,k)>(g-f) then g*d_h(f,k)/(d_h(f,k)-(g-f*10^-3))
else infinity end_if):
...

d_f(50,5.6,100) results in infinity like coded in the if statment
above.

But when I try the following plot It won't work. But why?

p56f:=plot::Function3d(d_f(f,5.6,g),f=10..300,g=0.01..1000):
Error: Can't evaluate to boolean [_less];
during evaluation of 'd_f'

Because your code does not handle the call “d_f(f,5.6,g)” which you have given. This is not really something about plotting. You get the same error message from just typing “d_f(f,5.6,g)“. Try
p56f:=plot::Function3d(hold(d_f(f,5.6,g)),f=10..300,g=0.01..1000)
instead.


regards,
	Christopher Creutzig
	(who starts thinking if it would break
	 anything to include an implicit hold()
	 at this place, since the problem keeps
	 confusing users)
.

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