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| #include <cstdio> | |
| #include <stdexcept> | |
| template <class T> | |
| struct Maybe { | |
| Maybe( const T& val ) : val_(val), valid_(true) { } | |
| Maybe() : valid_(false) { } | |
| const T& get() const { | |
| if (valid_) return val_; | |
| throw std::logic_error("lol type systems"); | |
| } | |
| private: | |
| T val_; | |
| bool valid_; | |
| }; | |
| template <class T> | |
| Maybe<T> Just(const T& val) { | |
| return Maybe<T>(val); | |
| } | |
| template <class T> | |
| Maybe<T> Nothing() { | |
| return Maybe<T>(); | |
| } | |
| Maybe<int> isYouPositive(int x) | |
| { | |
| if (x > 0) return Just(x); | |
| return Nothing<int>(); | |
| } | |
| int main(void) | |
| { | |
| auto a = isYouPositive(1); | |
| printf("%d\n", a.get()); | |
| auto b = isYouPositive(-1); | |
| printf("%d\n", b.get()); | |
| } | |
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