#10747: symbolic functions can be defined with a constant argument
----------------------------------------------------------+-----------------
Reporter: pang | Owner:
burcin
Type: defect | Status:
needs_review
Priority: minor | Milestone:
sage-4.7.1
Component: misc | Resolution:
Keywords: symbolic function, assignment, sd31 | Work_issues:
Upstream: N/A | Reviewer:
Author: Burcin Erocal, Zafeirakis Zafeirakopoulos | Merged:
Dependencies: |
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Changes (by newvalueoldvalue):
* status: new => needs_review
* author: => Burcin Erocal, Zafeirakis Zafeirakopoulos
* cc: boothby (added)
* component: symbolics => misc
* keywords: symbolic function, assignment => symbolic function,
assignment, sd31
Old description:
> The expression
> {{{
> h(6)=8
> }}}
> currently defines a symbolic function ``h`` with constant value 8. This
> makes no sense, but begginers make this mistake, for example if h is an
> array and they use () instead of []. It doesn't hurt to throw an error at
> all expressions
> {{{
> h(something) = ...
> }}}
> whenever something is not a symbolic variable.
New description:
The expression
{{{
h(6)=8
}}}
currently defines a symbolic function ``h`` with constant value 8. This
makes no sense, but begginers make this mistake, for example if h is an
array and they use () instead of []. It doesn't hurt to throw an error at
all expressions
{{{
h(something) = ...
}}}
whenever something is not a symbolic variable.
Apply [attachment:trac_10747-preparse_calculus.2.patch],
[attachment:trac_10747-preparser-docstrings-symbolic-vars.patch]
--
Comment:
It seems the real problem is in the preparser. Normally, when `f(1)=2` is
preparsed on the command line, it becomes `f(Integer(1))=Integer(2)`. This
is not valid python so we get an error anyway. In the notebook, the
constants are extracted and assigned to variables named `_sage_const_*`.
Then the `preparse_calculus()` function receives
`f(_sage_const_2)=sage_const_3` as input, which is a valid construction.
[attachment:trac_10747-preparse_calculus.2.patch] changes
`preparse_calculus()` to raise an error if the argument name starts with
`sage.misc.preparser.numeric_literal_prefix`.
[attachment:trac_10747-preparser-docstrings-symbolic-vars.patch] adds
doctest for the errors on the command line and the notebook.
It would be better if someone more familiar with the preparser reviewed my
patch.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10747#comment:6>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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