#4498: Implement a symbolic version of the arg function
--------------------------------------------------+-------------------------
Reporter: TimothyClemans | Owner: somebody
Type: enhancement | Status:
needs_review
Priority: major | Milestone:
sage-wishlist
Component: symbolics | Keywords: beginner,
sd35.5
Work_issues: random tests, Maxima | Upstream: N/A
Reviewer: Karl-Dieter Crisman, Burcin Erocal | Author: Karen T.
Kohl, Burcin Erocal
Merged: | Dependencies:
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Changes (by newvalueoldvalue):
* status: needs_work => needs_review
* author: Karen T. Kohl => Karen T. Kohl, Burcin Erocal
Old description:
> It would be nice if there were a symbolic arg function, just like the
> symbolic sin, cos, etc., functions. Then the following would happen:
>
> {{{
> sage: f = arg(x); f
> arg(x)
> sage: f.subs(x=1+I)
> arg(1+I)
> }}}
>
> Now we have
> {{{
> sage: arg(1+I)
> 0.785398163397
> sage: type(arg(1+I))
> <type 'sage.rings.real_double.RealDoubleElement'>
> }}}
>
> I.e., the arg in Sage is currently the numerical person's arg, not the
> symbolic person's. It just casts to CDF.
>
> "The function should return the argument of a complex function." - Ronan
> Paixão
New description:
It would be nice if there were a symbolic arg function, just like the
symbolic sin, cos, etc., functions. Then the following would happen:
{{{
sage: f = arg(x); f
arg(x)
sage: f.subs(x=1+I)
arg(1+I)
}}}
Now we have
{{{
sage: arg(1+I)
0.785398163397
sage: type(arg(1+I))
<type 'sage.rings.real_double.RealDoubleElement'>
}}}
I.e., the arg in Sage is currently the numerical person's arg, not the
symbolic person's. It just casts to CDF.
"The function should return the argument of a complex function." - Ronan
Paixão
Apply
* attachment:trac_4498-symbolic_arg.cleanup.patch
* attachment:trac_4498-arg_evalf.patch
--
Comment:
Apparently I didn't run tests, latex output was also broken.
attachment:trac_4498-arg_evalf.patch, to be applied after
attachment:trac_4498-symbolic_arg.cleanup.patch, implements a new
`_evalf_()` function which keeps the precision of the input. This one
needs a real review. :)
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4498#comment:19>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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