Question: "eval" results in "vector index out of range"

Hey Everybody,

I have only been using Maple for a few weeks but have been very much enjoying the functionality of the with(VectorCalculus) tools. That said, I have been having some trouble evaluating vectors at specific values.

> with(VectorCalculus);
> P[0] := PositionVector([t, ln(t)]);
> N[0] := PrincipalNormal(P[0], t);
> P := eval(P[0], t = 1);

> N := eval(N[0], t = 1);
 
> P[0];
Error, Vector index out of range
> PlotPositionVector(P[0], t = 0 .. 2, tangent = true, normal = true, points = [1], 'curveoptions' = [scaling = constrained]);
Error, Vector index out of range

However, If I do not 'eval', the last commands execute just fine. Is there a way to 'eval' without changing the vectors I am evaluating?

Thanks in advance!