#12554: Adding a "swap" method to equation objects.
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Reporter: JoalHeagney | Owner: AlexGhitza
Type: enhancement | Status: new
Priority: minor | Milestone: sage-5.0
Component: algebra | Keywords: swap, left hand side, right hand
side, inequalities
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Often when working with sage equations, it's desirable to swap the left
and right hand side of the equations. (Makes substitutions easier for a
start, allows manual solving of inequalities, etc.)
A model implementation by Ivan Andrus
[https://groups.google.com/forum/#!topic/sage-support/lKbMSQrFhGg]
(in function form) is supplied below (with some rearrangement so equal
operator case is tested first):
{{{
import operator
def reverse_inequality(eq):
"""
Reverse the order of the inequality without changing it's meaning.
"""
orig_op = eq.operator() # The "top-level" operator
if orig_op == operator.eq:
op = operator.eq
elif orig_op == operator.lt:
op = operator.gt
elif orig_op == operator.le:
op = operator.ge
elif orig_op == operator.gt:
op = operator.lt
elif orig_op == operator.ge:
op = operator.le
elif orig_op == operator.ne:
op = operator.ne
else:
raise TypeError, "this expression must be a relation"
return op(eq.rhs(), eq.lhs())
}}}
My request is that something similar be attached to equation objects as a
method.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12554>
Sage <http://www.sagemath.org>
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