On Jan 24, 2008 11:36 AM, "Martin v. Löwis" <[EMAIL PROTECTED]> wrote: > > trunc() has well-defined semantics -- it takes a Real instance and > > converts it to an Integer instance using round-towards-zero semantics. > > No. trunc calls __trunc__, which does whatever it pleases to do. > > >>> class A: > ... def __trunc__(self): > ... return 0 > ... > >>> a=A() > >>> trunc(a) > 0
However, PEP 3141 specifies what it should do for Numbers. > > int() has undefined semantics -- it takes any object and converts it > > to an int (a concrete type!) using whatever rules it likes -- the > > definition of __int__ is up to whatever the source type likes to do. > > For float this has been defined the same as trunc() above, but for > > other types, who knows! int() of a string does something completely > > different. > > But why is that a reason to keep trunc()? If you only ever want to > convert floats to ints, you can use either one, with no difference. > int() does *not* have undefined semantics, for floats, it converts > it to an integer using round-towards-zero semantics. Yes (although it wasn't always specified this way). But I don't like that, because of the ambiguity of int(x). -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
