On Wed, Apr 30, 2008 at 12:28 AM, Yann Le Du <[EMAIL PROTECTED]> wrote: > > Hello, > > First, the function oct does not work properly, it seems. > > oct(2345) fails in Sage (but works in Python) > oct(int(2345)) works > hex(2345) works > > Irc said it was the preparser. Why would the input of oct be preparsed > correctly and not that of hex ?
I think you asked this question backwards. Anyway, the problem is that nobody implemented __oct__ for Sage integers, but they did implement __hex__. Note that oct(...) calls __oct__: sage: a = 2345 sage: a.__hex__() '929' sage: a.__oct__() --------------------------------------------------------------------------- <type 'exceptions.AttributeError'> Traceback (most recent call last) /Users/was/<ipython console> in <module>() <type 'exceptions.AttributeError'>: 'sage.rings.integer.Integer' object has no attribute '__oct__' In the meantime you can do either sage: oct(int(a)) '04451' or sage: a.digits(8) [1, 5, 4, 4] or sage: a.str(base=8) '4451' I've opened a trac ticket so that __oct__ will get implemented soon for the integers: http://trac.sagemath.org/sage_trac/ticket/3062 > Sage uses notions from abstract algebra. I never use abstract algebra when > doing my coding in physics. I guess software like Mathematica kind of > guesses the best way to proceed with the input I give. Now, this guess > might not be the most appropriate. > > So I'd be grateful if anyone had some suggestions for a book on abstract > algebra that would teach me the practical usage of rings, fields, etc. > from a computational point of view ; something like "common computational > errors and fallacies corrected by an abstract algebra approach", something > that would build upon ideas like "1/3 + 1/10**20 - 1/3" is better done in > the the rationals than in the floats. Maybe some book similar to Forman > Acton's books that would explicitly use notions of abstract algebra. > > I had a look at Schaum's Modern Abstract Algebra by Ayres, 2004, but > comments on amazon mentioned multiple errors, opacities and out of > datedness. Irc suggested wikipedia. Any other suggestion ? I don't know of any such books, though I'm interested to check out David Joyner's book, which he advertised in this thread. William --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] 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 -~----------~----~----~----~------~----~------~--~---
