#10682: sum fails with lower bound != 0 or 1 (upgrade maxima to 5.26)
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Reporter: fmaltey
| Owner: burcin
Type: defect
| Status: needs_work
Priority: critical
| Milestone: sage-5.0
Component: symbolics
| Keywords:
Work_issues: several doctests need to be patched due to changes in output
format/term order | Upstream: N/A
Reviewer:
| Author:
Merged:
| Dependencies:
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Comment(by nbruin):
Replying to [comment:32 jpflori]:
> Anyway, isn't there something in Maxima which "knows" that a variable is
real after such assumptions ?
It's just a little weak in its deductions:
{{{
(%i1) domain: complex;
(%o1) complex
(%i2) display2d: false;
(%o2) false
(%i3) sqrt(x^2);
(%o3) sqrt(x^2)
(%i4) assume(x>0);
(%o4) [x > 0]
(%i5) sqrt(x^2);
(%o5) x
(%i6) sqrt(4/x^2);
(%o6) sqrt(4/x^2)
(%i7) domain:real;
(%o7) real
(%i8) sqrt(4/x^2);
(%o8) 2/x
}}}
It is ingrained now that the calculus maxima runs with `domain: complex`,
so if you want to temporarily switch to `domain: real`, you should switch
back afterwards. In principle this could play havoc with multiple threads,
but maxima is not threadsafe anyway and our signal management isn't
compatible with ECL's ideas of dealing with threads either. So, if in
`desolve` (conditional on domain="real") we just do:
{{{
P("load('contrib_ode)")
...
try:
P("domain: real")
soln = P(cmd)
finally:
P("domain: complex")
}}}
we should be fine (the "try ... finally" should guard that we end up with
`domain: complex`). I don't think performance is a concern if we're doing
a "load" every time anyway!.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10682#comment:40>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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