Simple issue. I think it is a bug, but if not, it tends to cause logic problems with new users of Maple.
z := A*x*y:
plot3d(z, x=0..1, y=0..1); # works as expected
contourplot(z, x=0..1, y=0..1); # works
fieldplot(z, x=0..1, y=0..1);
--> Error, (in plots/fieldplo) invaled 1st argument (the function) 1.0*x*y
Is there something special about what the fieldplot expects for the function? I don't see it in the help. Or is this a bug?
Yes, there is a work around, define all constants first
A:=1.0: z := A*x*y: fieldplot(z, x=0..1, y=0..1);
But I fail to understand why my example should fail. (Note, I have seen this situation for every version, so it is not new.)