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Task/Y-combinator/EchoLisp/y-combinator.echolisp

@@ -0,0 +1,23 @@
+;; Ref : http://www.ece.uc.edu/~franco/C511/html/Scheme/ycomb.html
+
+ (define Y
+    (lambda (X)
+      ((lambda (procedure)
+         (X (lambda (arg) ((procedure procedure) arg))))
+       (lambda (procedure)
+         (X (lambda (arg) ((procedure procedure) arg)))))))
+
+; Fib
+(define Fib* (lambda (func-arg)
+    (lambda (n) (if (< n 2) n (+ (func-arg (- n 1)) (func-arg (- n 2)))))))
+(define fib (Y Fib*))
+(fib 6)
+    → 8
+
+; Fact
+(define F*
+   (lambda (func-arg) (lambda (n) (if (zero? n) 1 (* n (func-arg (- n 1)))))))
+(define fact (Y F*))
+
+(fact 10)
+    → 3628800