On Wed, Jun 1, 2016 at 1:56 PM, Jeroen Demeyer <jdeme...@cage.ugent.be> wrote: > On 2016-05-31 20:35, Robert Bradshaw wrote: >> >> I can't think of any fundamental reason these couldn't be implemented >> in C, but there's really no need to do so as they can't be overridden >> in C. > > > Well, for the comma operator there might be no reason. However, it would be > nice if one could generate arbitrary code of the form > > (x) (operator) (y) > > for any C/C++ values x and y and any operator. Two particular cases I > encountered where this would be useful: > > 1. "x = y" where x is something that Cython does not consider an lvalue.
Cython doesn't support operator= even for C++, nor provide an operator.X definition for it. (These are only provided for operators that don't have a Python equivalent.) Are there cases in C where one has an lvalue but Cython can't tell? (I suppose foo(x) if foo is a macro--is that the only case?) You can always define your own macro #define ASSIGN(a, b) (a = b). Redefining what a valid lvalue is in the language (and syntax) is a whole can of worms I'd rather avoid getting into... > 2. "x || y" because Cython's "x or y" generates complicated code which isn't > optimized as well as "x || y". I just tried using gcc -O3 and the resulting assembly is identical. Granted, "x or y" does have a different meaning in Python (and Cython), returning the first of x or y that is True rather than a boolean. To get the C behavior, write <bint>(x or y). I think this is automatically done when it's used as a condition. The "more complicated" code is necessary to get the correct short-circuiting behavior, in particular when the right hand side is not expressible as a pure C expression (e.g. requires intermediates). - Robert _______________________________________________ cython-devel mailing list cython-devel@python.org https://mail.python.org/mailman/listinfo/cython-devel
