#9935: Make a symbolic mod function
-----------------------------+------------------------
Reporter: jason | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-6.4
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
-----------------------------+------------------------
Description changed by jdemeyer:
Old description:
> A participant in the PREP program noticed that mod is not a symbolic
> function:
>
> {{{
> sage: mod(x,4)
> 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', (4562, 0))
>
> 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', (4530, 0))
>
> 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', (842, 0))
>
> ---------------------------------------------------------------------------
> TypeError Traceback (most recent call
> last)
>
> /home/grout/sage-4.5.2/devel/sage-main/sage/functions/<ipython console>
> in <module>()
>
> /home/grout/sage/local/lib/python2.6/site-
> packages/sage/rings/finite_rings/integer_mod.so in
> sage.rings.finite_rings.integer_mod.Mod
> (sage/rings/finite_rings/integer_mod.c:2633)()
>
> /home/grout/sage/local/lib/python2.6/site-
> packages/sage/rings/finite_rings/integer_mod.so in
> sage.rings.finite_rings.integer_mod.IntegerMod
> (sage/rings/finite_rings/integer_mod.c:2952)()
>
> /home/grout/sage/local/lib/python2.6/site-
> packages/sage/rings/finite_rings/integer_mod.so in
> sage.rings.finite_rings.integer_mod.IntegerMod_int.__init__
> (sage/rings/finite_rings/integer_mod.c:14249)()
>
> /home/grout/sage/local/lib/python2.6/site-
> packages/sage/structure/parent.so in
> sage.structure.parent.Parent.__call__ (sage/structure/parent.c:6407)()
>
> /home/grout/sage/local/lib/python2.6/site-
> packages/sage/structure/coerce_maps.so in
> sage.structure.coerce_maps.NamedConvertMap._call_
> (sage/structure/coerce_maps.c:4053)()
>
> /home/grout/sage/local/lib/python2.6/site-
> packages/sage/symbolic/expression.so in
> sage.symbolic.expression.Expression._integer_
> (sage/symbolic/expression.cpp:4026)()
>
> TypeError: unable to convert x (=x) to an integer
> }}}
>
> Hopefully it should be easy to wrap mod in a symbolic function, something
> like:
>
> {{{
> sage: def eval_mod(self, x):
> ....: if isinstance(x, (int, Integer)):
> ....: return mod(x,5)
> ....: return None
> ....:
> sage: f=function('f', eval_func=eval_mod)
> sage: f(x)
> f(x)
> sage: f(13)
> 3
> sage: f(x^2+x+1)
> f(x^2 + x + 1)
> sage: f(x^2+x+1).subs(x=2)
> 2
> sage: f(x^2+x+1).subs(x=3)
> 3
> sage: f(x^2+x^3).subs(x=1)
> 2
> sage: f(x^2+x^3).subs(x=2)
> 2
> sage: f(x^2+x^3).subs(x=3)
> 1
> }}}
New description:
A participant in the PREP program noticed that mod is not a symbolic
function:
{{{
sage: mod(x,4)
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', (4562, 0))
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', (4530, 0))
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', (842, 0))
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/home/grout/sage-4.5.2/devel/sage-main/sage/functions/<ipython console> in
<module>()
/home/grout/sage/local/lib/python2.6/site-
packages/sage/rings/finite_rings/integer_mod.so in
sage.rings.finite_rings.integer_mod.Mod
(sage/rings/finite_rings/integer_mod.c:2633)()
/home/grout/sage/local/lib/python2.6/site-
packages/sage/rings/finite_rings/integer_mod.so in
sage.rings.finite_rings.integer_mod.IntegerMod
(sage/rings/finite_rings/integer_mod.c:2952)()
/home/grout/sage/local/lib/python2.6/site-
packages/sage/rings/finite_rings/integer_mod.so in
sage.rings.finite_rings.integer_mod.IntegerMod_int.__init__
(sage/rings/finite_rings/integer_mod.c:14249)()
/home/grout/sage/local/lib/python2.6/site-
packages/sage/structure/parent.so in sage.structure.parent.Parent.__call__
(sage/structure/parent.c:6407)()
/home/grout/sage/local/lib/python2.6/site-
packages/sage/structure/coerce_maps.so in
sage.structure.coerce_maps.NamedConvertMap._call_
(sage/structure/coerce_maps.c:4053)()
/home/grout/sage/local/lib/python2.6/site-
packages/sage/symbolic/expression.so in
sage.symbolic.expression.Expression._integer_
(sage/symbolic/expression.cpp:4026)()
TypeError: unable to convert x (=x) to an integer
}}}
Hopefully it should be easy to wrap mod in a symbolic function, something
like:
{{{
sage: def eval_mod(self, x):
....: if isinstance(x, (int, Integer)):
....: return mod(x,5)
....: return None
....:
sage: f=function('f', eval_func=eval_mod)
sage: f(x)
f(x)
sage: f(13)
3
sage: f(x^2+x+1)
f(x^2 + x + 1)
sage: f(x^2+x+1).subs(x=2)
2
sage: f(x^2+x+1).subs(x=3)
3
sage: f(x^2+x^3).subs(x=1)
2
sage: f(x^2+x^3).subs(x=2)
2
sage: f(x^2+x^3).subs(x=3)
1
}}}
See also [http://ask.sagemath.org/question/25037/declaring-variable-to-
be-in-a-particular-fieldringgroup/]
--
--
Ticket URL: <http://trac.sagemath.org/ticket/9935#comment:7>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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