Functional C++ examples

functional.cpp

#include <iostream>
#include <cassert>
#include <functional>
#include <algorithm>

class Callable {
public:
	int operator()(int x) { return x + 1; };
};

const auto is_even = [](int x) -> bool
{
	return x % 2 == 0;
};

std::function<int(int)> add_curried(int a)
{
	return [a](int b)
	{
		return a + b;
	};
};

template <typename T>
void print(T t)
{
	std::cout << t << std::endl;
}

int main(void)
{
	assert(is_even(2) == true);
	assert(is_even(3) == false);
	assert(is_even(4) == true);
	
	Callable callable_object;
	
	print(callable_object(1));

	int val = 42;
	const auto add_value = [val](auto x)
	{
		return x + val;
	};

	print(add_value(1));
	print(add_value(1.1));
	print(add_curried(3)(4));

	std::vector<int> data{1, 2, 3, 4, 5};
	std::vector<int> results(data.size());

	std::transform(data.begin(), data.end(), results.begin(), [](int x)
				   { return x + 1; });

	for (int num : results)
	{
		print(num);
	}

	return 0;
}