#17130: Fix coercion bugs in symbolic functions
-------------------------------------+-------------------------------------
Reporter: jdemeyer | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.4
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: Jeroen Demeyer | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jdemeyer/ticket/17130 | b6e1ed44a663f7410fddb2e3e4c134aa3a0ce8cf
Dependencies: #17131, #17133 | Stopgaps:
-------------------------------------+-------------------------------------
Description changed by jdemeyer:
Old description:
> This uses coercion correctly:
> {{{
> sage: bessel_Y._eval_(RealField(300)(1), 1.0)
> -0.781212821300289
> }}}
>
> However, it seems that `__call__()` coerces this result back to the first
> parent, giving false precision:
> {{{
> sage: bessel_Y(RealField(300)(1), 1.0)
> -0.781212821300288684511770043172873556613922119140625000000000000000000000000000000000000000
> }}}
>
> Same issue with functions which are evaluated using Maxima, which does
> not support arbitrary precision:
> {{{
> sage: R=RealField(300); elliptic_eu(R(1/2), R(1/8))
> 0.495073732023201484864216581627260893583297729492187500000000000000000000000000000000000000
> }}}
>
> The `gamma_inc()` function also mishandles parents:
> {{{
> sage: gamma_inc(float(0), float(1))
> AttributeError: type object 'float' has no attribute 'precision'
> }}}
>
> Possible follow-ups: #10133, #14766
New description:
This uses coercion correctly:
{{{
sage: bessel_Y._eval_(RealField(300)(1), 1.0)
-0.781212821300289
}}}
However, it seems that `__call__()` coerces this result back to the first
parent, giving false precision:
{{{
sage: bessel_Y(RealField(300)(1), 1.0)
-0.781212821300288684511770043172873556613922119140625000000000000000000000000000000000000000
}}}
Same issue with functions which are evaluated using Maxima, which does not
support arbitrary precision:
{{{
sage: R=RealField(300); elliptic_eu(R(1/2), R(1/8))
0.495073732023201484864216581627260893583297729492187500000000000000000000000000000000000000
}}}
The `gamma_inc()` function also mishandles parents:
{{{
sage: gamma_inc(float(0), float(1))
AttributeError: type object 'float' has no attribute 'precision'
}}}
----
Apart from this, this branch also removes lots of boilerplate from
`_eval_` like
{{{
if not isinstance(x, Expression) and not isinstance(y, Expression) and \
(is_inexact(x) or is_inexact(y)):
x, y = coercion_model.canonical_coercion(x, y)
return self._evalf_(x, y, s_parent(x))
}}}
by wrapping `_eval_` inside the new method `_evalf_or_eval_` which
automatically does this boilerplate.
----
Possible follow-ups: #10133, #14766
--
--
Ticket URL: <http://trac.sagemath.org/ticket/17130#comment:30>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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