> > Another way to think of this: subs is basically just mapping through > some kind of homomorphism. Yes. It is (a partially defined) homomorfism from a (categorically) free object to something else.
Freeness is the key here. So the following is somewhat confusing in my current implementation. sage: s=NumberField(x^2+1,'s').gen() sage: (1+s).subs(s=1) s + 1 The substitution rightfully does not happen as s is not a free variable (there is no __call__ method). Maybe an exception should be raised in the following case: the element has no __call__ method but a ParentWithGens. and some of the variables to be substituted are among the generators. But perhaps this makes subs too expensive for a rather small gain in usability. Michel --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
