Opened 12 years ago

Last modified 5 years ago

#6480 new defect

.subs_expr() method doesn't work for argument of D derivative operator — at Initial Version

Reported by: gmhossain Owned by:
Priority: major Milestone: sage-8.0
Component: symbolics Keywords:
Cc: kcrisman, mjo, eviatarbach, jakobkroeker Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

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Description

In computing functional derivative, one needs to vary a functional. For example, in sage-3.4 one can do as follows

sage: f(x) = function('f',x)
sage: df(x) = function('df',x)
sage: g = f(x).diff(x)
sage: g
diff(f(x), x, 1)
sage: g.subs_expr(f(x)==f(x)+df(x))
diff(f(x) + df(x), x, 1)

In new symbolics, if I do the same I get

sage: g
D[0](f)(x)
sage: g.subs_expr(f(x)==f(x)+df(x))
D[0](f)(x)

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