functional-cpp

Header-only tools for functional programming in C++

It provides the following features:

---

Partial function application

int add(int a, int b) {
  return a + b;
}
  
// ...

const auto add2 = partial::apply(add, 2);
const auto five = add2(3);

---

Optional values with Option

It exposes two variants, Some(T) and None.

Usage:

using option::Option;
using option::Some;
using option::None;

const Option<int> some_opt = Some(42);
const Option<int> none_opt = None;

const auto mapped_opt = some_opt.map(Map(x, x*2)); // Some(84)

const auto some_value = some_opt.value();
const auto none_value = none_opt.value_or(42);

auto divide(int a, int b) -> Option<int> {
  return (b != 0) ? Some(a/b) : None;
}

---

Error handling with Result

Result<T, U> represents the result of an operation that can fail. It exposes two variants, Ok(T) and Err(U).

Usage:

using result::Result;
using result::Ok;
using result::Err;

auto foo() -> Result<int, bool> {
  return Ok(42);
}

auto bar() -> Result<int, bool> {
  return Err(false);
}