#12650: Perform safe simplifications in Expression.simplify()
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Reporter: mjo | Owner: mjo
Type: enhancement | Status: new
Priority: major | Milestone: sage-5.0
Component: symbolics | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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This is part 1 (of n, n >= 1) of an attempt to make simplification safer.
Right now, `simplify()` doesn't attempt anything drastic: it sends the
expression to Maxima and back. So if you want a non-trivial
simplification, you have to use something else.
That something else is `full_simplify()`, unless you want to write your
own simplification function. But `full_simplify()` has a problem: the evil
radcan.
1. #3520 - inconsistency in simplify_radical
2. #12322 - invalid simplification of complex logarithm
3. [http://ask.sagemath.org/question/767/simplification-errors-in-simple-
expressions AskSage 767] - simplification errors in simple expressions
And a simple example that logix was nice enough to dig out of my code on
IRC:
{{{
sage: f = sqrt((x+1)^2)
sage: f.full_simplify()
x + 1
sage: f(x = -5)
4
sage: f.full_simplify()(x = -5)
-4
}}}
The goal is to make simplification safer, through some combination of,
* Making `simplify()` more useful.
* Making it obvious that `full_simplify()` can do some, uh,
''unintuitive'' things.
Unless there are objections, I see no reason not to make `simplify()`
perform all "safe" simplifications; that is, simplifications for which
`simplify(expr) == expr` with some certainty.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12650>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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