#17793: wrong piecewise convolution
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Reporter: rws | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.5
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by rws:
Old description:
> This doctest tests against a wrong result, the resulting curve must have
> a quadratic part:
> {{{
> sage: f = piecewise([[(-1,1),1]])
> ## example 2
> sage: g = piecewise([[(0,3),x]])
> sage: f.convolution(g)
> Piecewise defined function with 3 parts, [[(-1, 1), 0], [(1,
> 2), -3/2*x], [(2, 4), -3/2*x]]
> }}}
> The ticket is for documentary reasons because a new piecewise code is
> being worked on in #14801.
New description:
This doctest tests against a wrong result, the resulting curve must have a
quadratic part:
{{{
sage: f = piecewise([[(-1,1),1]])
## example 2
sage: g = piecewise([[(0,3),x]])
sage: f.convolution(g)
Piecewise defined function with 3 parts, [[(-1, 1), 0], [(1,
2), -3/2*x], [(2, 4), -3/2*x]]
}}}
From numerical investigation it seems the solution would be
`piecewise(x|-->1/2*x^2 + x + 1/2 on (-1/2, 1), x|-->2*x on (1, 2),
x|-->-1/2*x^2 + x + 4 on (2, 7/2); x)`.
The ticket is for documentary reasons because a new piecewise code is
being worked on in #14801.
--
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Ticket URL: <http://trac.sagemath.org/ticket/17793#comment:2>
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