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On Wed, 14 Jan 2015 23:23:54 -0800 Andrew Robinson <andrew3@r3dsolutions.com> wrote: > > > Boolean algebra has two values: true and false, or 1 and 0, or humpty > > and dumpty, or whatever you like to call them. > You're speaking to an Electrical engineer. I know there are 10 kinds of > people, those who know binary and those who don't. But you're way off > base if you think most industrial quality code for manipulating boolean > logic uses (or even can be restricted to use) only two values and still > accomplish their tasks correctly and within a finite amount of time. > [snip] Absolutely it does and can. You store anything that's non-boolean in a non-boolean value, and keep it as fuzzy as you like. But at the end of the day, an if statement has no "kinda". You do, or you don't. 1 or 0. And so you must ultimately resolve to a Boolean decision. > > > > Can you name any other language that *does* allow subclassing of > > booleans or creation of new boolean values? > Yes. Several off the top of my head -- and I have mentioned these > before. They generally come with the extra subclasses pre-created and > the user doesn't get to create the classes, but only use them; none the > less -- they have more than two values with which to do logic equations > with. > > VHDL, Verilog, HDL, Silos III, and there are IEEE variants also. > C/C++ historically allowed you to do it with instances included, > although I am not sure it still does. > Incorrect, at least in VHDL. If I've got "signal x : boolean;", then x is defined on the range (true, false). I can ask VHDL "if x then; ...; end if;" What you're talking about is not at all a subclass of boolean, it's a std_logic. It's a separate enumerated type, with a set of resolution rules defined in a function the source of which is available in std_logic_1164.vhd. And according to the strict rules of VHDL (up until VHDL2008 decided to forfeit some purity for simplicity's), you can't simply have: signal x: std_logic ... if x then You have to ask if x = '1' or if (x = '1') or (x = 'H') Because you are comparing one value of an enumerated type against others, the result of that '=' operation being, in fact, a boolean, defined again on the range (true, false). > [snip] > > We've discovered that we live in a quantum-mechanical universe -- yet > people still don't grasp the pragmatic issue that basic logic can be > indeterminate at least some of the time ?! > But actions can't be. You're not asking the software about it's feelings, you're telling it to follow a defined sequence of instructions. Do this, or don't do this. > I don't know what you mean about composition vs. sub-classing. > Would you care to show an example of how it would solve the problem and > still allow hierarchical sorting ? > > I don't see how you can get pre-existing python functions (like sort, > max, and min) to accept a complex bool value and have that value > automatically revert to a True or False in an intelligent manner without > overloading the operators defined in some class -- somewhere -- to > operate on the data the class contains. > > How do you intend to achieve that with this -- composition -- thing you > mentioned ? > > You'd do it something like this. class _clogic(object): """Represents 'continuous' logic. For any given instance, there is a threshold value between 0 and 1 that delineates True from False, with 0 being entirely False and 1 being entirely True. """ def __init__(self, value, threshold=0.5): self.value = value self.threshold = threshold def __bool__(self): return value > threshold __nonzero__ = __bool__ def __eq__(self, other): if other in (True, False): return bool(self) == other try: return self.value == other.value except AttributeError: return self.value == other def __and__(self, other): return self.__class__( min(self.value, other.value), self.threshold) def __or__(self, other): return self.__class__( max(self.value, other.value), self.threshold) No need to subclass bool, you just use the __bool__ (or __nonzero__) methods to say "Alright, well when you do finally have to make a decision on this thing, here's how you make it. And obviously, you can add on as many additional data members to carry additional information as your heart desires. -- Rob Gaddi, Highland Technology -- www.highlandtechnology.com Email address domain is currently out of order. See above to fix.
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Re: Comparisons and sorting of a numeric class.... Andrew Robinson <andrew3@r3dsolutions.com> - 2015-01-12 17:59 -0800
Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve@pearwood.info> - 2015-01-13 05:32 +0000
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-13 17:13 +1100
Re: Comparisons and sorting of a numeric class.... Terry Reedy <tjreedy@udel.edu> - 2015-01-13 05:49 -0500
Re: Comparisons and sorting of a numeric class.... Marko Rauhamaa <marko@pacujo.net> - 2015-01-13 13:00 +0200
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-13 22:20 +1100
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-13 11:56 -0700
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-14 06:02 +1100
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-13 21:56 +1100
Re: Comparisons and sorting of a numeric class.... Andrew Robinson <andrew3@r3dsolutions.com> - 2015-01-13 16:12 -0800
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-14 01:31 -0700
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-14 22:26 -0700
Re: Comparisons and sorting of a numeric class.... Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-16 22:23 +1300
Re: Comparisons and sorting of a numeric class.... Andrew Robinson <andrew3@r3dsolutions.com> - 2015-01-14 23:23 -0800
Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve@pearwood.info> - 2015-01-15 08:41 +0000
Re: Comparisons and sorting of a numeric class.... Andrew Robinson <andrew3@r3dsolutions.com> - 2015-01-15 17:45 -0800
Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-16 18:33 +1100
Re: Comparisons and sorting of a numeric class.... Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-01-17 00:07 +1300
Re: Comparisons and sorting of a numeric class.... Rustom Mody <rustompmody@gmail.com> - 2015-01-16 03:22 -0800
Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-17 23:27 +1100
Re: Comparisons and sorting of a numeric class.... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-01-16 02:27 +0000
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-15 22:01 -0700
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-16 17:58 +1100
Re: Comparisons and sorting of a numeric class.... Rob Gaddi <rgaddi@technologyhighland.invalid> - 2015-01-15 09:54 -0800
Re: Comparisons and sorting of a numeric class.... Andrew Robinson <andrew3@r3dsolutions.com> - 2015-01-26 15:47 -0800
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-26 18:50 -0700
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-15 10:05 -0700
Re: Comparisons and sorting of a numeric class.... Andrew Robinson <andrew3@r3dsolutions.com> - 2015-01-23 03:46 -0800
Re: Comparisons and sorting of a numeric class.... Rustom Mody <rustompmody@gmail.com> - 2015-01-23 07:31 -0800
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-23 09:50 -0700
Re: Comparisons and sorting of a numeric class.... Rustom Mody <rustompmody@gmail.com> - 2015-01-23 09:03 -0800
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-24 04:23 +1100
Re: Comparisons and sorting of a numeric class.... Rustom Mody <rustompmody@gmail.com> - 2015-01-23 09:29 -0800
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-23 11:04 -0700
Re: Comparisons and sorting of a numeric class.... Rustom Mody <rustompmody@gmail.com> - 2015-01-23 19:13 -0800
Re: Comparisons and sorting of a numeric class.... Rustom Mody <rustompmody@gmail.com> - 2015-01-23 19:21 -0800
Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-24 16:01 +1100
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-24 16:43 +1100
Re: Comparisons and sorting of a numeric class.... Rustom Mody <rustompmody@gmail.com> - 2015-01-23 09:22 -0800
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-24 04:37 +1100
Re: Comparisons and sorting of a numeric class.... Rustom Mody <rustompmody@gmail.com> - 2015-01-23 09:45 -0800
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-24 05:03 +1100
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-23 11:13 -0700
Re: Comparisons and sorting of a numeric class.... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-24 19:27 +1100
Re: Comparisons and sorting of a numeric class.... Chris Angelico <rosuav@gmail.com> - 2015-01-23 22:58 +1100
Re: Comparisons and sorting of a numeric class.... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-01-23 12:07 +0000
Re: Comparisons and sorting of a numeric class.... Terry Reedy <tjreedy@udel.edu> - 2015-01-23 11:17 -0500
Re: Comparisons and sorting of a numeric class.... Ian Kelly <ian.g.kelly@gmail.com> - 2015-01-23 11:00 -0700
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