I think what he meant to say was that you can't override it with some __method__. The same holds for the ternary operator (as I mentioned in my previous reply).
Aaron Meurer On Fri, Jun 10, 2011 at 5:36 PM, Ronan Lamy <ronan.l...@gmail.com> wrote: > Le vendredi 10 juin 2011 à 16:29 -0700, Vinzent Steinberg a écrit : >> On 9 Jun., 23:31, Aaron Meurer <asmeu...@gmail.com> wrote: >> > Yeah, surely there was a typo when you typed this. The expression as >> > given is not syntactically correct Python (you can't assign to x|y). >> > Or else I (and I think everyone else too) is misunderstanding what you >> > meant to say. >> >> Sorry for the confusion, it was not meant to be Python. It would >> translate to this code: >> >> a = x | y >> assert a == x if x else y >> >> Or longer: >> >> if x: >> a = x >> else: >> a = y >> >> > > I'm not sure what you're suggesting here. This looks like a programming >> > > construct, which already exists in Python: 'x or y'. If it's meant to >> > > return a symbolic expression, I'd say too much is implicit here and we >> > > should rather use something like If(Ne(x, 0), x, y). >> >> In Python this does not work with 'or', because 'or' always returns >> either True or False, just like 'in'. > > No, it doesn't: >>>> 42 or '6*9' > 42 >>>> 0 or '6*9' > '6*9' > >> (I would prefer to use 'or' >> rather than '|'.) If you allowed 'or' to return an object, all boolean >> logic would still work, and you could do some fancy expressive stuff. >> Taken from a recent Go review [1]: >> >> """ >> Many people shun it, but the ?: ternary operator is a good idea, if >> used correctly. Python does foo if bar else baz, which is a little >> more verbose but still okay. Most dynamic languages, however, rock >> with their boolean operators AND and OR not just evaluating to true >> and false, but to the actual value that was considered true. Imagine >> the assignment value = cmdline_option || "default". That requires a >> decent boolean interpretation of all data types, however. >> """ >> >> Well, whether this is a good idea is arguable. Ronan, you will >> probably think it is a bad idea, I guess. :) >> >> > And like "and" and "or", I don't think you can override the >> > triconditional. "A if B else C" just evaluates bool(B) and returns A >> > if it is True and C if it is False. >> >> This is exactly what I wanted to happen. >> >> Vinzent >> >> >> [1] http://www.syntax-k.de/projekte/go-review >> > > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To post to this group, send email to sympy@googlegroups.com. > To unsubscribe from this group, send email to > sympy+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/sympy?hl=en. > > -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
