sum and product inside a program

[Helge Gabert]

I got strange results in one of my programs and it appears that sum() and product() don't work correctly, if called inside a program.

Example:
POLY(n,z)
BEGIN
LOCAL k;

sum(z^k/k^n, 1, 3, 1);
END;

returns +inf for POLY(2,.1).

But in CAS, from the command line, sum(0.1^k/k^2), returns .1026 . . .

Similar problem with product inside a program.

[roadrunner]

I could never get sum() to work right inside a program unless I made it a CAS program. This seems to do what you need:

#cas
POLY(n,z):=
BEGIN
LOCAL k;
sum(z^k/k^n,k,1,3,1);
END;
#end

-road

[Helge Gabert]

Thanks! I'll try that.

[Bill_McDonough]

Per Cyrille:

sum is sum(expr, var, reals...)... this program is missing an EXPORT and a k in the sum to work.
EXPORT POLY(n,z)
BEGIN
LOCAL k;
sum(z^k/k^n, k, 1, 3, 1);
END;

[Helge Gabert]

Yes, thanks for pointing this out - - I noticed that I forgot the index variable k as soon as I started on the CAS version a while back. All is well.