[with patch, positive review] Horrible bug in old (and new) symbolic calculus: f(x)=1; f*e --> BOOM!

[was]

On Sun, Jan 18, 2009 at 7:08 AM, YannLC  wrote:
>
> but in fact the same error occurs without ns=1...
>
> ----------------------------------------------------------------------
> | Sage Version 3.2.3, Release Date: 2009-01-05                       |
> | Type notebook() for the GUI, and license() for information.        |
> ----------------------------------------------------------------------
> sage: f(x)=1
> sage: f*e
> [...]
> RuntimeError: maximum recursion depth exceeded

That is weird.  What a horrible bug!   Thanks for reporting this.  It is now trac #

It also happens with ns=1. I've verified this.

[mhansen]

Note that the new code doesn't get run as doing

f(x) = 1

overwrites the old x (which was created with var('x',ns=1)) with just var('x'). The infinite recursion is due the CallableSymbolicExpression? ring assuming that all elements of SR were instances of SymbolicExpression?.

[was]

Looks good. Great work fixing this so quickly!

[mabshoff]

Merged in Sage 3.3.alpha0