Mike Hansen wrote: >> The best I've come up with at this point is, given graphs A,B,C,D,E, the >> union is: >> >> A.union(B).union(C).union(D).union(E) >> >> where the union function returns the modified graph each time so I can >> keep chaining union function calls. The union actually modifies the >> graph A, so if you want A left alone and a new graph returned, you do: >> >> newgraph=A.copy().union(B).union(C).union(D).union(E) >> >> Comments? Is there a better way to do things? > > I think A.union(B) should leave A and B unchanged and return a new > graph object since that's pretty much how everything else works in > Python. In-place operations feel very out-of-place ;-)
That's what I always thought to. But then I saw the Python sort() function, or the reverse() function, etc. and grudgingly accepted that the python way was to modify things in place. In the end, I want two options: to modify things in-place or to return a new object. I also want some sort of consistency so that the user isn't constantly guessing what a function will do. After playing with things for a bit, I decided that the easiest consistent thing to do was to modify in-place and call A.copy().whatever() when I wanted to return a new object. That way a copy was explicitly denoted with somewhat minimal syntax, the general case was consistent, and we still had access to both options. Would you suggest doing things the other way? Return a new copy by default and always have: A=A.union(B) to modify A? It's slightly worse performance-wise, it seems, because we are always making copies and throwing old copies away. Especially if we have the above (A.union(B).union(C).union(D).union(E))---then we make 4 new copies of things and throw away all but 1 of them. -Jason --~--~---------~--~----~------------~-------~--~----~ 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/ -~----------~----~----~----~------~----~------~--~---
