On Sun, 01 Jul 2012 05:55:24 -0400, Terry Reedy wrote: > On 7/1/2012 2:54 AM, Steven D'Aprano wrote: > >> So no, Python has always included chained comparisons, and yes, it is >> shameful that a language would force you to unlearn standard notation >> in favour of a foolish consistency with other operators. Comparisons >> aren't special because they return bools. They are special because of >> the way they are used. >> >> C treats comparison operators as if they were arithmetic operators, and >> so the behaviour of a chained comparison is the same as the behaviour >> as a sequence of arithmetic operators: a foolish consistency. Python >> treats comparison operators as comparison operators, and gives them >> behaviour appropriate to comparisons. > > I considered this a great feature of Python when I first learned it. > Reading about how rare it is among programming languages to treat > comparisons in the standard way in mathematics reinforces that.
Apart from Python, Mathematica, Perl 6, CoffeeScript, Cobra and Clay give chained comparisons the standard meaning. It is, or was, a feature request for Boo, but I can't tell whether it has been implemented or not. C-like semantics are next to useless, except perhaps for obfuscation: http://stackoverflow.com/questions/4089284/why-does-0-5-3-return-true/ And surprising: http://answers.yahoo.com/question/index?qid=20090923172909AA4O9Hx C-like semantics are a clear case of purity of implementation overruling functional usefulness. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
