ExpandVisitor does not process arguments of FunctionSymbol

[salehjg]

Hi there,

I was experimenting with expand(foo, true) and noticed that ExpandVisitor is not expanding the arguments of symbolic functions (FunctionSymbol).

For example with Sympy:

import sympy as sp
>>> e1 = sp.parse_expr("f(2*(x+y)*(x-y))")
>>> e1
f((x - y)*(2*x + 2*y))
>>> sp.expand(e1)
f(2*x**2 - 2*y**2)

but this is not possible with SymEngine::expand(), or I am missing something quite obvious.

I modified ExpandVisitor by adding this method to make it work for now:

void bvisit(const FunctionSymbol &x) {
    vec_basic args;
    for (auto &arg: x.get_args()) {
        args.push_back(expand(arg));
    }
    auto e = function_symbol(x.get_name(), args);
    Add::dict_add_term(d_, multiply, e);
}

I am using a patched version of SymEngine 0.10.1 on Arch.

Could you please advise me on how to handle FunctionSymbols properly?

Best,
Saleh