An (experimental) implementation of Scala-like function objects in C++11 that support currying.
C C++
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Better Function Objects in C++

An (experimental) implementation of Scala-like function objects in C++11 that support currying:

#include "function_object.h"

int sum_(int i, int j) {
	return i + j;
auto sum = make_function_object(sum_); // sum is a binary function

int main() {
	// sum can be called like any binary function:
	std::cout << " 5 + 4 = " << sum(5, 4) << "\n";

	// if you supply only one argument, sum turns into a unary function:
	auto increment = sum(1);
	std::cout << " increment(5) = " << increment(5) << "\n";


See the function_object header and check out the examples in main.cpp. It isn't much code. If you create function objects out of lambdas or callable objects you have to specify the arity. There is currently no way to derive the function signatur from a callable object in C++. All I can do is check if an object can be called with a given signature, but that is not the same thing.

It compiles successfully with GCC 4.8.2 It does not compile with Visual Studio 2013 at the moment.

To Do

Function objects cannot be chained. That is obviously useful. It would allow you to create a function object like this:

auto unary_func = ternary_function( some_unary_function, 4, 5 ); 

Calling unary_func(x) should expand to ternay_function(some_unary_function(x), 4, 5).


The idea came to me while listening to Eric Niebler's Keynote speech at this year's Meeting C++ conference. He had experimented with function objects and recommended writing them. We are using them at think-cell because they are easier to use in std::bind statements. I wondered if it was possible to extend to support currying.