The principle of least surprise would suggest that mutability should follow the same rules independent of the matrix size. And echelon_form should always return an immutable matrix.
On Saturday, August 1, 2015 at 1:51:12 AM UTC+2, Andrey Novoseltsev wrote: > > Hello, > > While working on http://trac.sagemath.org/ticket/18613 I ran into the > following problem: > > sage: matrix(2, 1).echelon_form().is_mutable() > False > sage: matrix(2, 0).echelon_form().is_mutable() > True > > i.e. while usually echelon_form returns an immutable matrix this is not > the case with trivial ones. The reason is in the beginning of its code: > > if self._nrows == 0 or self._ncols == 0: > self.cache('pivots', ()) > self.cache('rank', 0) > if transformation: > return self, self > return self > > The question is how to fix it: > 1) make here a copy of self, set it to be immutable, and return it > 2) make self immutable and return self > 3) always make matrices without elements immutable (not sure if this can > be done in one place or in several implementations) > > It seems that 3) is the most sensible, but what if some code checks for > the ability to change a matrix a refuses to work with immutable ones? Any > suggestions? > > Thank you! > Andrey > > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
