#9724: Sage allows creation of variables with empty name
----------------------------+-----------------------------------------------
Reporter: logix | Owner: burcin
Type: defect | Status: new
Priority: minor | Milestone: sage-4.5.3
Component: symbolics | Keywords: variable empty name
Author: Harold Gutch | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
----------------------------+-----------------------------------------------
Sage allows you to create a variable with an empty name. While this at
first appears not to cause any problems, one thing it does break is
reset():
{{{
sage: var(' ')
(, )
sage: whos
Variable Type Data/Info
----------------------------------
Expression
sage: reset()
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (437, 0))
---------------------------------------------------------------------------
IndexError Traceback (most recent call
last)
/usr/local/sage/local/lib/python2.6/site-packages/sage/all_cmdline.pyc in
<module>()
/usr/local/sage/local/lib/python2.6/site-packages/sage/misc/reset.so in
sage.misc.reset.reset (sage/misc/reset.c:838)()
IndexError: string index out of range
sage: del globals()['']
sage: reset()
}}}
Sage also allows the creation of variables with other illegal names (e.g.
'1a' or '1'), but for these at least reset() still works. There are two
ways to fix this, the first is to disallow the creation of such variables
via var(), but then all illegal cases would have to be taken care of, and
it wouldn't help if you created illegal variables manually by inserting
them into globals() (but I would argue that if you do this, you're on your
own anyway). The second way to fix the behaviour above would be to make
reset() able to delete empty variables too. This however is only viable
if these variables don't break anything else, other than the case
mentioned above.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9724>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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