symbolic constants in CAS

[jgreenb2]

A few learnings but no solution. First, CAS is based is giac. This must be common knowledge but not to me! Which means, of course, that Parisse is actually Bernard Parisse -- Hello! So that explains how to find the "missing" documentation on CAS (like what are the legitimate arguments to assume(), etc.).

So I downloaded a version of XCAS and tried to see what to do. There, it works exactly as I want:

laplace(exp(a*x),x,t) returns -((1/(a-t))) with no complaints about the symbol 'a'.

That gives me hope it should be possible on the prime, but again, how???