Solving a single equation for multiple variables doesn't work with assumptions

[rburing]

As reported in Ask SageMath question #46915:

sage: x,y = var('x,y', domain=RR)
sage: solve(x == 0, x, y)

gives an error message (unlike variants without assumptions, solving for a single variable, or adding a dummy equation).

It can be traced as follows: in sage/symbolic/relation.py the function solve calls _solve_expression to handle the single expression case. This (by default) uses the Maxima interface to create an initial list of solutions X, which is then filtered according to assumptions(). This filtering assumes that each solution in X is a single equation (it calls .lhs() on elements of X), which is not true in the case of multiple variables.

Component: symbolics

Keywords: solve, assumptions, domain

Issue created by migration from https://trac.sagemath.org/ticket/27998

[embray]

comment:1

Moving open critical and blocker issues to the next release milestone (optimistically).

[embray]

comment:2

Ticket retargeted after milestone closed

[mkoeppe]

comment:3

Moving tickets to milestone sage-9.2 based on a review of last modification date, branch status, and severity.

[mkoeppe]

comment:5

Moving to 9.4, as 9.3 has been released.