[Python-Dev] A macro for easier rich comparisons

[David Malcolm]

On Tue, 2015-04-28 at 10:50 -0700, Glenn Linderman wrote:
> On 4/28/2015 2:13 AM, Victor Stinner wrote:
> 
> > > #define Py_RETURN_RICHCOMPARE(val1, val2, op)                               \
> > > >     do {                                                                    \
> > > >         switch (op) {                                                       \
> > > >         case Py_EQ: if ((val1) == (val2)) Py_RETURN_TRUE; Py_RETURN_FALSE;  \
> > > >         case Py_NE: if ((val1) != (val2)) Py_RETURN_TRUE; Py_RETURN_FALSE;  \
> > > >         case Py_LT: if ((val1) < (val2)) Py_RETURN_TRUE; Py_RETURN_FALSE;   \
> > > >         case Py_GT: if ((val1) > (val2)) Py_RETURN_TRUE; Py_RETURN_FALSE;   \
> > > >         case Py_LE: if ((val1) <= (val2)) Py_RETURN_TRUE; Py_RETURN_FALSE;  \
> > > >         case Py_GE: if ((val1) >= (val2)) Py_RETURN_TRUE; Py_RETURN_FALSE;  \
> > > >         }                                                                   \
> > > >         Py_RETURN_NOTIMPLEMENTED;                                           \
> > > >     } while (0)
> > I would prefer a function for that:
> > 
> > PyObject *Py_RichCompare(long val1, long2, int op);
> Why would you prefer a function?  As a macro, when the op is a
> constant, most of the code would be optimized away by a decent
> compiler.
> 
> I suppose when the op is not a constant, then a function would save
> code space.
> 
> So I suppose it depends on the predominant use cases.

There's also the possibility of wrapping C++ code that uses overloaded
operators: having it as a macro could allow those C++ operators to be be
mapped into Python.

Hope this is constructive
Dave