#15021: Return unevaluated derivative from BuiltinFunction
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Reporter: eviatarbach | Owner:
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:
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Comment (by nbruin):
This issue was discussed before. We have the functionality in
`FDerivativeOperator`, it's just not available on top level or as a method
on BuiltinFunction instances:
[http://permalink.gmane.org/gmane.comp.mathematics.sage.devel/58041]
I thought this stuff was on trac somewhere already, but I cannot find it
presently. For archival purposes:
{{{
from sage.symbolic.operators import FDerivativeOperator
class Doperator:
def __init__(self,vars=None):
self.vars= [] if vars is None else vars
def __call__(self,f):
return FDerivativeOperator(f,self.vars)
def __getitem__(self,i):
if isinstance(i,tuple):
newvars=self.vars+list(i)
else:
newvars=self.vars+[i]
return Doperator(newvars)
D=Doperator()
}}}
With that code one can input the form that sage prints:
{{{
sage: var('x,y')
sage: D[0](f)(x, y)/x + D[0, 1](f)(x, y)
D[0](f)(x, y)/x + D[0, 1](f)(x, y)
}}}
Input will never be in Leibnitz notation, since unevaluated functions do
not have names for their parameters, just position numbers for them.
--
Ticket URL: <http://trac.sagemath.org/ticket/15021#comment:6>
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