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Add missing %python:maybecall to operator overloads.

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This ensures NotImplemented is returned on error so that the Python
interpreter will handle the operators correctly instead of throwing an
exception. NotImplemented was not being returned for non-builtin wrappers
when the operator overload did not have a function overload.

See PEP 207 and https://docs.python.org/3/library/constants.html#NotImplemented

Mentioned in SF patch #303 and SF bug #1208.
This commit is contained in:
William S Fulton 2017-06-19 19:12:23 +01:00
commit 687cf9c9c1
4 changed files with 98 additions and 6 deletions
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Doc/Manual/Python.html
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@ -1894,6 +1894,14 @@ Also, be aware that certain operators don't map cleanly to Python. For instance
overloaded assignment operators don't map to Python semantics and will be ignored.
</p>
<p>
Operator overloading is implemented in the <tt>pyopers.swg</tt> library file.
In particular overloaded operators are marked with the <tt>python:maybecall</tt> feature, also known as <tt>%pythonmaybecall</tt>.
This feature forces SWIG to generate code that return an instance of Python's <tt>NotImplemented</tt>
instead of raising an exception when the comparison fails, that is, on any kind of error.
This follows the guidelines in <a href="https://www.python.org/dev/peps/pep-0207/">PEP 207 - Rich Comparisons</a> and <a href="https://docs.python.org/3/library/constants.html#NotImplemented">NotImplemented Python constant</a>.
</p>
<H3><a name="Python_nn25">36.3.12 C++ namespaces</a></H3>