#13586: BuiltinFunction expects to be instantiated only once
-------------------------------------+--------------------------------------
Reporter: burcin | Owner: burcin
Type: defect | Status: positive_review
Priority: major | Milestone: sage-5.5
Component: symbolics | Resolution:
Keywords: symbolic function | Work issues:
Report Upstream: N/A | Reviewers: Karl-Dieter Crisman
Authors: Burcin Erocal | Merged in:
Dependencies: | Stopgaps:
-------------------------------------+--------------------------------------
Changes (by kcrisman):
* status: needs_review => positive_review
* reviewer: => Karl-Dieter Crisman
Old description:
> From [[http://ask.sagemath.org/question/1843/weird-behavior-
> builtinfunction|this ask.sagemath.org question]]:
>
> {{{
> sage: from sage.symbolic.function import BuiltinFunction
> sage: class AFunction(BuiltinFunction):
> ....: def __init__(self, name, exp=1):
> ....: self.exponent=exp
> ....: BuiltinFunction.__init__(self, name, nargs=1)
> ....: def _eval_(self, arg):
> ....: return arg**self.exponent
> ....:
> sage: p2 = AFunction('p2', 2)
> sage: p2(x)
> x^2
> sage: p3 = AFunction('p3', 3)
> sage: p3(x)
> x^2
> }}}
>
> ATM, we only allow a `BuiltinFunction` to be instantiated once.
New description:
From [[http://ask.sagemath.org/question/1843/weird-behavior-
builtinfunction|this ask.sagemath.org question]]:
{{{
sage: from sage.symbolic.function import BuiltinFunction
sage: class AFunction(BuiltinFunction):
....: def __init__(self, name, exp=1):
....: self.exponent=exp
....: BuiltinFunction.__init__(self, name, nargs=1)
....: def _eval_(self, arg):
....: return arg**self.exponent
....:
sage: p2 = AFunction('p2', 2)
sage: p2(x)
x^2
sage: p3 = AFunction('p3', 3)
sage: p3(x)
x^2
}}}
ATM, we only allow a `BuiltinFunction` to be instantiated once.
----
Apply [attachment:trac_13586-builtin_function.patch].
--
Comment:
Nice work, Burcin. I guess this doesn't stop someone from doing
{{{
sage: p4 = AFunction('p2',3)
}}}
but I suppose that is the user's problem, since they are redefining the
name `p2`. Similarly, is this (new behavior, I think) ok? I think so,
but just want to make sure.
{{{
sage: class MyFunction(BuiltinFunction):
....: def __init__(self,name):
....: self.exponent=1
....: BuiltinFunction.__init__(self,name,nargs=1)
....: def _eval_(self,arg):
....: return arg**self.exponent
....:
sage: MyFunction('p')
p
sage: p = MyFunction('p')
sage: p
p
sage: p(2)
2
sage: p(3)
3
sage: q = MyFunction('q')
sage: q(3)
3
sage: p
p
sage: q
q
}}}
----
Patchbot: Apply trac_13586-builtin_function.patch
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13586#comment:2>
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