On Jan 24, 2008 10:36 AM, Raymond Hettinger <[EMAIL PROTECTED]> wrote: > Can anyone explain to me why we need both trunc() and int()?
trunc() has well-defined semantics -- it takes a Real instance and converts it to an Integer instance using round-towards-zero semantics. 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. Perhaps worse is that sometimes int() is lossy (e.g. with a float input) and sometimes it is not (e.g. with a string input, or with a non-standard representation of integers). There are still some places where a float is accepted incorrectly (silently truncating) due to the use of the __int__ slot. If trunc() had been part of the language from the beginning we wouldn't have needed to introduce __index__. -- --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
