On Thursday, March 13, 2014 3:05:22 PM UTC-7, Lee Worden wrote:
>
> sage: s = symbolic_expression( 'a(x)' )
> sage: s.substitute_function(
> sage.symbolic.function_factory.function('a'),
> sage.symbolic.function_factory.function('A') )
> A(x)
> sage: t = deepcopy( s )
>
Since symbolic expressions are not mutable, you shouldn't have a need to
make deep copies of them. The behaviour does seem problematic, though.
The problem you are seeing stems from:
sage: sage.symbolic.function_factory.function('a') == s.operator()
True
sage: sage.symbolic.function_factory.function('a') == t.operator()
False
It looks like deep copy is a little too eager: it shouldn't make a copy of
the function 'a', but it does. You end up with a different function
(accessible via t.operator() ) which also prints as 'a' but isn't equal to
the function 'a' you can create via
sage.symbolic.function_factory.function. Basically, you got what you asked
for: a COPY of the function, not the function itself.
Something fishy is going on, though, because
sage: a=s.operator()
sage: deepcopy(a)
a
sage: deepcopy(a) == a
True
sage: deepcopy(a) is a
False
sage: deepcopy(a)(x).substitute_function(
....: sage.symbolic.function_factory.function('a'),
....: sage.symbolic.function_factory.function('A') )
A(x)
so a function object by itself does get "deepcopied" correctly, but when
it's sitting in an expression it is not.
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