Add fixed point combinator #372

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1. jbgi commented on Oct 26, 2018

   

   jbgi

   on Oct 26, 2018

   MemberAuthor

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   Here is what I have in mind:

     static <A> A fix(F<A, A> f, F<F0<A>, A> delay) {
       return new Object() {
         final A a = delay.f(() -> f.f(this.a));
       }.a;
     }

     static <A, B> F<A, B> rec(F<F<A, B>, F<A, B>> f, F<F0<B>, B> delay) {
       return new F<A, B>() {
         final F<A, B> rec = f.f(this);
         @Override
         public B f(A a) {
           return delay.f(() -> rec.f(a));
         }
       };
     }

   Does that make sense?