def __call__(self, *args):
"""
EXAMPLES::
sage: from sage.symbolic.operators import FDerivativeOperator
sage: x,y = var('x,y')
sage: f = function('foo')
sage: op = FDerivativeOperator(f, [0,1])
sage: op(x,y)
diff(foo(x, y), x, y)
sage: op(x,x^2)
D[0, 1](foo)(x, x^2)
TESTS:
We should be able to operate on functions evaluated at a
point, not just a symbolic variable, :trac:`12796`::
sage: from sage.symbolic.operators import FDerivativeOperator
sage: f = function('f')
sage: op = FDerivativeOperator(f, [0])
sage: op(1)
D[0](f)(1)
"""
if (not all(is_SymbolicVariable(x) for x in args)
or len(args) != len(set(args))):
# An evaluated derivative of the form f'(1) is not a
# symbolic variable, yet we would like to treat it
# like one. So, we replace the argument `1` with a
# temporary variable e.g. `t0` and then evaluate the
# derivative f'(t0) symbolically at t0=1. See trac
# #12796.
temp_args = SR.temp_var(n=len(args))
vars = [temp_args[i] for i in self._parameter_set]
return self._f(*temp_args).diff(*vars).function(*temp_args)(*args)
vars = [args[i] for i in self._parameter_set]
return self._f(*args).diff(*vars)
