"William Stein" <[EMAIL PROTECTED]> writes: > On Tue, Oct 14, 2008 at 4:15 AM, Martin <[EMAIL PROTECTED]> wrote: > > > > Am I doing something wrong in the session below? > > I guess so, given the error messages. > > > I admit that I do not understand python types and methods yet. When > > can I apply the functional notation, when the method notation? It > > It's not just notation. Python supports both functions and methods, > and they are just completely different things.
I probably should have asked: why doesn't R after sage: R=Set(range(0,20,2)) have a parent method? I thought that parent is defined by Sage... Maybe differently put: why is the result of Set fundamentally different from, say, the result of vector? (I'm trying to say: "fundamentally different" with respect to their properties as Python objects) One difference I can see is that vector returns a type, and Set a class, but I couldn't find a definitive answer on the web. http://www.python.org/download/releases/2.2.3/descrintro/ says: Python 2.2 introduces the first phase of "type/class unification". This is a series of changes to Python intended to remove most of the differences between built-in types and user-defined classes. but I guess I'm misunderstanding something here, since sage.modules.vector_integer_dense.Vector_integer_dense is certainly not built-in... sage: type(vector([1,2,3])) <type 'sage.modules.vector_integer_dense.Vector_integer_dense'> sage: type(Set([1,2,3])) <class 'sage.sets.set.Set_object_enumerated'> Please help! Not sure, whether it's a similar question: why doesn't Primes() export intersect, union, etc. Is this a design decision, a language problem, or just because it's not yet implemented? > > seems that it's not a language thing, because they often return > > different things. > > It is a language thing, I think. It would be great if you could give me a hint. > > As another example, Mod(5,3) and mod(5,3) seem to > > agree, while 5.mod(3) is different and 5.Mod(3) is an error. I could not find an answer to that question in "Dive into Python", not in the python reference. Are you saying that Integer Ring cannot implement a Mod method, or that it should not? > > Is a method responsible for checking whether it's arguments are ofthe > > right type/parent, or is there a possibility to restrict the > > arguments to a given type/parent? > > You should really read the free book "Dive into Python". It's great (and > free). Well, looking at this book, I got the impression that the answer to my question is "yes, it's the methods responsibility and no, there is no other possibility". I was hoping for a different answer, but if it's that way, that's OK, too. I'm very sorry if my questions are stupid, but it's really hard for me to grasp the way things work in Sage and Python. Until recently I thought that FriCAS and Sage would be relatively similar, it seems to me now that they are extremely different. I hope I'm only having beginner's troubles. Hoping for your patience, Martin --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@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-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
