[issue12211] Better document math.copysign behavior.

[Terry J. Reedy]

Terry J. Reedy <tjreedy at udel.edu> added the comment:

Third party refers to things other than Pythonx.y code For instance, distutils2/distribute was for some years developed separately from the main codebase and was recently merged into the 3.3 repository. While separate, its issues were '3rd party'. That has nothing to do with this.

A patch against 3.2 is fine. It will almost certainly apply unchanged to both 3.3 and 2.7 since this part of the doc may have never changed since written. The patch looks fine so far. I see that you kept the line just under 80 characters. Now, can you expand it to also change the docstring for this function in the mathmodule.c file? I am not exactly sure where it is in the file, relative to the function code itself. As I remember, it is not as convenient as in Python files.
It currently looks like

    copysign(x, y)
    
    Return x with the sign of y.

When revising the "Return ..." part to match the doc, I think we should include the "On a platform ..." sentence also. If Mark disagrees, it would be easily removed. Notice that the indent is 1 or 2 more spaces, so the existing line would become too long. 'a platform' could be changed to 'platforms'. I personally like that better anyway.

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components: +Documentation -Library (Lib)
title: math.copysign must keep object type. -> Better document math.copysign behavior.
versions: +Python 2.7, Python 3.3

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<http://bugs.python.org/issue12211>
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