Y combinator: Difference between revisions

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   return YFunctor<A,B>(f);
 }</lang>
-{{works with|C++17}}
-<lang cpp>
-#include <stdio.h>
-template<typename FF,typename F>
-struct G;
-template<typename FF,typename RT,typename ...Args>
-struct G<FF,RT(Args...)> {
-    FF f;
-    struct Z {
-        G g;
-        constexpr Z(FF f) : g{f} {}
-        constexpr RT operator()(Args ...args)const{
-            return g.f(g())(args...);
-        }
-    };
-    constexpr Z operator()()const{
-        return Z{f};
-    }
-};
-template<typename F>
-struct _Y;
-template<typename RT,typename ...Args>
-struct _Y<RT(Args...)> {
-    template<typename F>
-    constexpr auto operator()(F f)const{
-        return [f](auto g){
-            return f(g());
-        }(G<F,RT(Args...)>{f});
-    }
-};
-template<typename F>
-constexpr auto Y=_Y<F>{};
-int main(){
-    constexpr auto almost_fac = [](auto f){
-        return [f](auto n,auto acc){
-            return (n == 0) ? acc : f(n-1,n*acc);
-        };
-    };
-    constexpr auto almost_fib = [](auto f){
-         return [f] (auto n) {
-             return n < 2? n: f (n - 1) + f (n - 2);
-         };
-    };
-    constexpr auto fac = Y<long(long,long)>(almost_fac);
-    constexpr auto fib = Y<long(long)>(almost_fib);
-    constexpr auto fac_10 = fac(10,1);
-    constexpr auto fib_10 = fib(10);
-    printf("%ld\n",fib_10);
-    printf("%ld\n",fac_10);
-}</lang>
-{{out}}
-<pre>
-3628800
-</pre>
 =={{header|Ceylon}}==