Nearly from the beginning, `solve` has recognized the `undetermined
coefficients` case wherein a single equation is solved for a set of symbols
which will simultaneously set it equal to zero. This is different than the
normal use of `solve`, however, and might be considered a bug or feature.
As an example, consider:
[in1] solve(a*x + b - (2*x + 4), (a, b)) # solve for a and b
{a: 2, b: 4}
[in2] solve(a*x + b - (2*x + 4), exclude=[x]) # solve for as many as
possible, but not x
{a: 2, b: 4}
[in3] solve(a*x + b - (2*x + 4), a) # solve for a
[(-b + 2*x + 4)/x]
[in4] solve(a*x + b - (2*x + 4)) # solve for anything and tell me what you
did
[{a: (-b + 2*x + 4)/x}]
The "undetermined coefficients" case is returned from inputs 1 and 2 while
the more usual "solution" is returned from 3 and 4.
The request for comment is whether this feature should be removed from
`solve` so a better defined equation set is provided rather than building
that equation set automatically when this case is detected as
one-equation-many-symbols.
To me it feels natural to get the undetermined coefficients solution when I
ask for many symbols from one equation. If I want sympy to pick any
variable other than some I would use `exclude=some` (where `some` is a list
or set of things to ignore). But not everyone feels this way and refusing
the temptation to guess is important, too.
Since this behavior is described in the docstring and has been present for
many years it feels like a regression of this feature to me (though to
others it feels like a bug fix). If you use this feature and/or have
comments, please let us know your thoughts on this:
1) should it be kept?
2) if removed, should there be deprecation?
Thanks,
Chris
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