#17890: Remove _(rich)cmp_c_impl
-------------------------------------+-------------------------------------
Reporter: jdemeyer | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.6
Component: cython | Resolution:
Keywords: | Merged in:
Authors: Jeroen Demeyer | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jdemeyer/ticket/17890 | 17bd067153ad40ced061147390687f514a7f7cba
Dependencies: | Stopgaps:
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Comment (by jdemeyer):
This is how Python implements `cmp`:
{{{
#!c
static int
do_cmp(PyObject *v, PyObject *w)
{
int c;
cmpfunc f;
if (v->ob_type == w->ob_type
&& (f = v->ob_type->tp_compare) != NULL) {
c = (*f)(v, w);
if (PyInstance_Check(v)) {
/* Instance tp_compare has a different signature.
But if it returns undefined we fall through. */
if (c != 2)
return c;
/* Else fall through to try_rich_to_3way_compare() */
}
else
return adjust_tp_compare(c);
}
/* We only get here if one of the following is true:
a) v and w have different types
b) v and w have the same type, which doesn't have tp_compare
c) v and w are instances, and either __cmp__ is not defined or
__cmp__ returns NotImplemented
*/
c = try_rich_to_3way_compare(v, w);
if (c < 2)
return c;
c = try_3way_compare(v, w);
if (c < 2)
return c;
return default_3way_compare(v, w);
}
}}}
Note how `tp_compare` is only called if the types of `v` and `w` are
equal. If not, `__richcmp__` is used. Only if `__richcmp__` is not
implemented, then `__cmp__` is tried after all.
--
Ticket URL: <http://trac.sagemath.org/ticket/17890#comment:42>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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