Problem wirt erf



Dear all,
I have been too lazy to search the documentation for the normal 
distribution and typed in:

A:integrate(exp(-w^2/2),w);
distri0(q):=float(subst(q,w,A));
distri(q):=float(1/sqrt(2*%pi)*(sqrt(%pi/2)-distri0(q)));

But then on Maxima 5.21.0 (the official binary gcl for windows) the 
calculation
distri(0);
yields the error message
Maxima encountered a Lisp error:
 Error in MACSYMA-TOP-LEVEL [or a callee]:
Error in CONDITIONS::CLCS-UNIVERSAL-ERROR-HANDLER [or a callee]: The 
slot CONDITIONS::DATUM is unbound in the object 
#<CONDITIONS::INTERNAL-TYPE-ERROR.2>.
Fast links are on: do (use-fast-links nil) for debugging
Broken at PCL::PRINT-STD-INSTANCE.  Type :H for Help.

On MuPAD the  similair definitions work as expected.
 
A:=int(exp(-w^2/2),w);
distri0:= q->float(subs(A,w=q));
distri:= q->float(1/sqrt(2*PI)*(sqrt(PI/2)-distri0(q)));

distri(0) yields 0.5

Any help on this issue?

Reinhard

-- 
Prof. Dr. Reinhard Oldenburg
Goethe-Universit?t Frankfurt
Institut f?r Didaktik der Mathematik und Informatik 
Senckenberganlage 9
D-60325 Frankfurt/Main
Telefon  +49 (0)69 798 23770
Telefax  +49 (0)69 798 22553
E-Mail   oldenbur at math.uni-frankfurt.de
WWW      www.math.uni-frankfurt.de/~oldenbur