Thank you for the explanation. Not being familiar with python, I had no way of knowing wether it was Sage or python. The examples in Sage tend to use x, y & z as variable symbols so I naturally used them, as well. The logical construct of "print bool (symbol = symbol) should then not be used, I take it, as it generates a keyword error? And = should be replaced with ==? What occurs then when an assumption is explicitly symbol = some other symbol or , again, is the proper usage to use ==?
Many Thanks! Mike On Apr 17, 12:32 pm, Robert Bradshaw <rober...@math.washington.edu> wrote: > On Apr 17, 2009, at 11:00 AM, MikeF wrote: > > > > > > > Hi All, > > > Newbie issue. > > > I'm new to Sage but was messing about with Westers logical inference > > problem ( x>=y, y>=z, z>=z) and then using == and = by itself in the > > bool function. I've simplified the logic and isolated what I believe > > to be an error in behavior, perhaps designed but ought to be warned > > against. I found no warning. > > > The function bool seems to always generate true when constructed as > > "print bool( x= some variable)". Perhaps it is the global variable > > usage. My work around is not to use the variable x within logical > > constructs. It may or may not relate to the equivalence problem in > > Wester. > > This is because the Python bool constructor names it's first argument > "x" and so x is getting passed in as a keyword argument. In pure Python: > > >>> bool(x=5) > True > >>> bool(x=None) > False > > Note that this is a common problem: > > >>> int(x=2) > 2 > > I'm not sure there's anything we can do about this (short of raising > a warning in the preparser, which IMHO is a bad idea). We could also > write our own is_true function, which doesn't accept keyword > arguments and passes on to bool. > > - Robert --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
