This is now http://trac.sagemath.org/ticket/19850
On 2016-01-08 18:16, Daniel Krenn wrote: > Dear all, > > from the method-name and also from the one-line description > "Return True if this symbolic expression is a constant." > of Expression.is_constant, I expected that this gives more or less the > same result as checking whether symbolic expression has an empty > .variables(). However, we have > sage: log(2).is_constant() > False > and also > sage: SR(2).is_constant() > False > only pi, e and that stuff is "constant". > I find this very confusing. Am I alone with this feeling? > > The above is also inconsistent to > sage: P.<p> = ZZ[] > sage: P(2).is_constant() > True > > Best wishes, > > Daniel > > PS: To be fair, after the one-line description, it is explained what it > really does: > This function is intended to provide an interface to query the > internal representation of the expression. In this sense, the word > "constant" does not reflect the mathematical properties of the > expression. Expressions which have no variables may return "False". > But the phrase "the internal representation of the expression" sounds > like the end user should not care about it... (i.e. this is_constant > could be an underscore-method...). > > PPS: At the moment (not having answers to this posting), my favourite > implementation would be something like > def is_constant(self): > return not self.variables() > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
