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Task/Y-combinator/Java/y-combinator-2.java

@@ -0,0 +1,23 @@
+import java.util.function.Function;
+
+public class YCombinator {
+    interface RecursiveFunc<F> extends Function<RecursiveFunc<F>, F> { }
+    public static <A,B> Function<A,B> fix(Function<Function<A,B>, Function<A,B>> f) {
+        RecursiveFunc<Function<A,B>> r = w -> f.apply(x -> w.apply(w).apply(x));
+        return r.apply(r);
+    }
+
+    public static void main(String[] args) {
+        Function<Integer,Integer> fib = fix(f -> n -> {
+		if (n <= 2) return 1;
+		return f.apply(n - 1) + f.apply(n - 2);
+            });
+        Function<Integer,Integer> fac = fix(f -> n -> {
+		if (n <= 1) return 1;
+		return n * f.apply(n - 1);
+	    });
+
+        System.out.println("fib(10) = " + fib.apply(10));
+        System.out.println("fac(10) = " + fac.apply(10));
+    }
+}