Is it possible to deduce the argument types of a functor?

Asked Apr 22 '16 at 15:55

Active Apr 22 '16 at 15:55

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Is it possible to deduce the argument types of a functor? For example:

struct foo {
    int operator()(double, std::string const&) const { return 0; }
};

template<class Foo>
struct bar
{
    using first_argument_type = /* type of the first argument of Foo::operator() */;
    using second_argument_type = /* type of the second argument of Foo::operator() */;
    using return_type = std::result_of_t<Foo(first_argument_type, second_argument_type)>;
};

asked Apr 22 '16 at 15:55

0xbadf00d

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Please assume that we know that `foo` has exactly two arguments and that there is no overload of `operator()`. – 0xbadf00d Apr 22 '16 at 15:56
Except if there are overloads, you can use some *function_traits*. – Jarod42 Apr 22 '16 at 15:56
See e.g. the [CallableTraits library](https://github.com/badair/callable_traits). – ildjarn Apr 22 '16 at 15:59

Is it possible to deduce the argument types of a functor?

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