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@cbsmith cbsmith/fmapp.hpp
Created Sep 5, 2018

What would you like to do?
A handy implementation of fmap that is apparently missing in the standard.
#include <optional>
namespace nonstd {
template <typename F, typename T>
auto fmap(F f, std::optional<T> x) -> std::optional<decltype(f(std::forward<T>(*x)))> {
return (x.has_value()) ?
std::make_optional(f(std::forward<T>(*x))) :
//be nice to senile programmers
template <typename T, typename F>
auto fmap(std::optional<T> x, F f) -> decltype(fmap(f, x)) {
return fmap(f, x);
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