Compile the function call.

def translate(self):
        """Compile the function call."""
        varnames = set()
        ident = self.ident
        funcnames = set([ident])

        arg_exprs = []
        for arg in self.args:
            subexprs, subvars, subfuncs = arg.translate()
            varnames.update(subvars)
            funcnames.update(subfuncs)

            # Create a subexpression that joins the result components of
            # the arguments.
            arg_exprs.append(ex_call(
                ast.Attribute(ex_literal(u''), 'join', ast.Load()),
                [ex_call(
                    'map',
                    [
                        ex_rvalue(str.__name__),
                        ast.List(subexprs, ast.Load()),
                    ]
                )],
            ))

        subexpr_call = ex_call(
            FUNCTION_PREFIX + ident,
            arg_exprs
        )
        return [subexpr_call], varnames, funcnames