Comment #11 on issue 1497 by asmeurer: Remove automatic distribution 2*(x +
y) => 2*x + 2*y
http://code.google.com/p/sympy/issues/detail?id=1497
Thinking about this, there are cases when this behavior is undefined, i.e.,
when there is a number multiplying
more than one Add:
In [1]: (x + y)*(z + n)
Out[1]: (x + y)⋅(n + z)
In [2]: 2*(x + y)*(z + n)
Out[2]: (n + z)⋅(2⋅x + 2⋅y)
In [3]: (x + y)*2*(z + n)
Out[3]: (n + z)⋅(2⋅x + 2⋅y)
In [4]: (x + y)*(z + n)*2
Out[4]: 2⋅(x + y)⋅(n + z)
In [5]: (z + n)*(x + y)
Out[5]: (x + y)⋅(n + z)
In [6]: 2*(z + n)*(x + y)
Out[6]: (x + y)⋅(2⋅n + 2⋅z)
In [7]: (z + n)*2*(x + y)
Out[7]: (x + y)⋅(2⋅n + 2⋅z)
In [8]: (z + n)*(x + y)*2
Out[8]: 2⋅(x + y)⋅(n + z)
And now that factor(2*x + 2*y) splits it into 2*(x + y) using
Mul(evaluate=False), there are problems with
issue 1864. So I am totally in favor of removing the automatic
distribution entirely. There is
expand(mul=True) if you want it, and maybe we could even write a special
case that only distributes numbers
if it is important.
The procedure outlined in comment 9 should "fix" it, but many tests will
need to be fixed. Hopefully no
algorithms rely on this automatic behavior, as was the case when I fixed
issue 252 (I had to put some
powsimp lines in the limit algorithm).
--
You received this message because you are listed in the owner
or CC fields of this issue, or because you starred this issue.
You may adjust your issue notification preferences at:
http://code.google.com/hosting/settings
--
You received this message because you are subscribed to the Google Groups
"sympy-issues" group.
To post to this group, send email to sympy-iss...@googlegroups.com.
To unsubscribe from this group, send email to
sympy-issues+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/sympy-issues?hl=en.
