On Apr 19, 2010, at 2:50 PM, wb wrote:
coming from C I'm confused about this behavior in assignment:
Since you know C, it may make sense to think of lists as being similar to pointers.
1) using only integers ---------------------------------- sage: a=2 sage: b=2 sage: b=b+a sage: b 4 sage: a 2 so (at least), after b=b+a, 'b' seems to have gotten its own instance, however 2) using lists ---------------------------------------------------- sage: a=[1,2] sage: b=a sage: b[0]=b[0]+a[0] sage: b [2, 2] sage: a [2, 2] <------- ?!? (which results also if done directly in python). So, after b[0]=b[0]+a[0], 'b' does not seem to get its own instance and 'a' therefore also gets modified ..!? ... which somehow seems inconsistent with 1) and very strange anyway ... Finally 3) ------------------------------------------------- sage: a=[1,2] sage: b=a+[] <------------ ! Trying to force (maybe?) an own instance for 'b' sage: b[0]=b[0]+a[0] sage: b [2, 2] sage: a [1, 2] <------------ ok in exmpl. 3) the list behaves similar to the integers in exmpl. 1). Question: is the assignment b=a+[] the only way to achieve this ? Thanks, wb -- 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 URL: http://www.sagemath.org
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