Re: how to overload operator (a x b)?
dmitrey wrote: is it possible to overload operator ? (And other like this one, eg = =, , = =) No. a x b is a shortcut for a x and x b where x is of course evaluated only once. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
Diez B. Roggisch de...@nospam.web.de wrote: Not really. I didn't get the chaining, and Peter is right that for that there is no real overloading. I'm sorry, I don't really get why overloading lt gt isn't an answer to the OP's question... His terminology may not have been correct but I'm not sure why it's not a sufficient response. (then again it is a Friday night and I have been out drinking...) -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
dmitrey schrieb: hi all, is it possible to overload operator ? (And other like this one, eg = =, , = =) Any URL/example? Thank you in advance, D. http://docs.python.org/reference/datamodel.html#object.__lt__ Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
On Fri, Aug 7, 2009 at 8:00 AM, dmitreydmitrey.kros...@scipy.org wrote: hi all, is it possible to overload operator ? (And other like this one, eg = =, , = =) Any URL/example? Thank you in advance, D. That isn't an operator at all. Python does not support compound comparisons like that. You have to do a b and b c. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
On Aug 7, 10:50 pm, Benjamin Kaplan benjamin.kap...@case.edu wrote: That isn't an operator at all. Python does not support compound comparisons like that. You have to do a b and b c. You know, it costs nothing to open up a python interpreter and check your certainty: x = 10 1 x 20 True This is a _very_ common pattern. class X(object): ... def __lt__(self, other): ... print 'in lt' ... return True ... def __gt__(self, other): ... print 'in gt' ... return True ... x = X() 1 x 20 in gt in lt True 20 x 1 in gt in lt True dmitrey: Diez' advice was the best you received. -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
alex23 schrieb: On Aug 7, 10:50 pm, Benjamin Kaplan benjamin.kap...@case.edu wrote: That isn't an operator at all. Python does not support compound comparisons like that. You have to do a b and b c. You know, it costs nothing to open up a python interpreter and check your certainty: x = 10 1 x 20 True This is a _very_ common pattern. class X(object): ... def __lt__(self, other): ... print 'in lt' ... return True ... def __gt__(self, other): ... print 'in gt' ... return True ... x = X() 1 x 20 in gt in lt True 20 x 1 in gt in lt True dmitrey: Diez' advice was the best you received. Not really. I didn't get the chaining, and Peter is right that for that there is no real overloading. Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
On Fri, 07 Aug 2009 08:50:52 -0400, Benjamin Kaplan wrote: On Fri, Aug 7, 2009 at 8:00 AM, dmitreydmitrey.kros...@scipy.org wrote: hi all, is it possible to overload operator ? (And other like this one, eg = =, , = =) Any URL/example? Thank you in advance, D. That isn't an operator at all. Python does not support compound comparisons like that. You have to do a b and b c. Python actually allows you to chain comparison operators, automatically unpacking ``a b c`` to ``a b and b c``:: class C(object): ... def __lt__(self, other): ... print self, LESS-THAN, other ... return True ... a = C(); b = C(); x = C() a x b __main__.C object... LESS-THAN __main__.C object... __main__.C object... LESS-THAN __main__.C object... True x = 42 40 x 50 # between 40 and 50 True 50 x 60 # between 50 and 60 False 1 == True 2 == 2.0 3 4 != 5 0 # yikes, unreadable! but legal. True # same as: (1 == True) and (True 2) and (2 == 2.0) ... HTH, -- Robert Stargaming Lehmann -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
Benjamin Kaplan wrote: Python does not support compound comparisons like that. You have to do a b and b c. Funny, my python does. This has been around a long time. I am not certain whether 1.5.2 did it, but chained comparisons have been around for a long time. 'a' 'd' 'z' True 'a' 'D' 'z' False --Scott David Daniels scott.dani...@acm.org -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
On 12:50 pm, benjamin.kap...@case.edu wrote: On Fri, Aug 7, 2009 at 8:00 AM, dmitreydmitrey.kros...@scipy.org wrote: hi all, is it possible to overload operator �? (And other like this one, eg = �=, �, = �=) Any URL/example? Thank you in advance, D. That isn't an operator at all. Python does not support compound comparisons like that. You have to do a b and b c. That's partially correct. There is no compound less than operator, or whatever you want to call that. However, Python does support compound comparisons like that: 1 2 3 True 1 3 2 False 1 == 2 == 3 False 2 == 2 == 2 True Jean-Paul -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
On Fri, 07 Aug 2009 08:04:22 -0700, Scott David Daniels wrote: Benjamin Kaplan wrote: Python does not support compound comparisons like that. You have to do a b and b c. Funny, my python does. This has been around a long time. I am not certain whether 1.5.2 did it, but chained comparisons have been around for a long time. Yes it does: $ python1.5 Python 1.5.2 (#1, Apr 1 2009, 22:55:54) [GCC 4.1.2 20070925 (Red Hat 4.1.2-27)] on linux2 Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam 2 3 4 1 Remembering that back then, 0 and 1 were used instead of False and True. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
On Aug 7, 7:18 am, Diez B. Roggisch de...@nospam.web.de wrote: alex23 schrieb: On Aug 7, 10:50 pm, Benjamin Kaplan benjamin.kap...@case.edu wrote: That isn't an operator at all. Python does not support compound comparisons like that. You have to do a b and b c. You know, it costs nothing to open up a python interpreter and check your certainty: x = 10 1 x 20 True This is a _very_ common pattern. class X(object): ... def __lt__(self, other): ... print 'in lt' ... return True ... def __gt__(self, other): ... print 'in gt' ... return True ... x = X() 1 x 20 in gt in lt True 20 x 1 in gt in lt True dmitrey: Diez' advice was the best you received. Not really. I didn't get the chaining, and Peter is right that for that there is no real overloading. You can program __lt__, __gt__, and friends to return a closure with a boolean value. See my upcoming reply to the author. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
Re: how to overload operator (a x b)?
On Aug 7, 9:01 pm, Carl Banks pavlovevide...@gmail.com wrote: On Aug 7, 7:18 am, Diez B. Roggisch de...@nospam.web.de wrote: alex23 schrieb: On Aug 7, 10:50 pm, Benjamin Kaplan benjamin.kap...@case.edu wrote: That isn't an operator at all. Python does not support compound comparisons like that. You have to do a b and b c. You know, it costs nothing to open up a python interpreter and check your certainty: x = 10 1 x 20 True This is a _very_ common pattern. class X(object): ... def __lt__(self, other): ... print 'in lt' ... return True ... def __gt__(self, other): ... print 'in gt' ... return True ... x = X() 1 x 20 in gt in lt True 20 x 1 in gt in lt True dmitrey: Diez' advice was the best you received. Not really. I didn't get the chaining, and Peter is right that for that there is no real overloading. You can program __lt__, __gt__, and friends to return a closure with a boolean value. See my upcoming reply to the author. Actually, scratch that. It won't work because the chained comparison short-circuits. If you have __lt__ return a closure then a b won't work unless a b is always true, which means it'll cause ordinary binary comparison to fail. Oh well. Carl Banks -- http://mail.python.org/mailman/listinfo/python-list
