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Description
This sage-support thread describes the following problem:
sage: var('y')
y
sage: (y==x).log()
log(y == x)
sage: (y==x).log().simplify() # just sends to Maxima and back to Sage
log(y) == log(x)
sage: (y==x).exp()
e^(y == x)
sage: (y==x).exp().simplify() # just sends to Maxima and back to Sage
TypeError: unable to make sense of Maxima expression 'e^(y=x)' in Sage
Basically, one can consider the problem in two ways - a Sage bug or a Maxima bug/feature. Depends on how you look at it.
- Option 1: We don't expect an = sign inside of expressions in our parser in sage/misc/parser.py. Once you leave Parser.p_eqn, there is a lot of jumping around that happens, but it never gets back there, and that is the only place that replaces = with ==. So we should fix that.
- Option 2: Maxima erroneously doesn't change
e^(y=x)toe<sup>y=e</sup>x. With log, it does:
sage: var('y'); a = (y==x).log()
sage: a._maxima_()
log(y)=log(x)
But with exp, it doesn't:
sage: var('y'); a = (y==x).exp()
y
sage: a._maxima_()
%e^(y=x)
For now putting the upstream as 'none of the above' since it's not clear the bug is upstream.
Upstream: Reported upstream. Developers deny it's a bug.
CC: @robertwb
Component: symbolics
Keywords: maxima parsing
Issue created by migration from https://trac.sagemath.org/ticket/11651