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Task/Power-set/EchoLisp/power-set.echolisp

@@ -0,0 +1,29 @@
+(define (set-cons a A)
+    (make-set (cons a A)))
+
+(define (power-set e)
+    (cond ((null? e)
+       (make-set (list ∅)))
+    (else (let [(ps (power-set (cdr e)))]
+       (make-set
+       (append ps (map set-cons (circular-list (car e)) ps)))))))
+
+(define B (make-set ' ( 🍎 🍇 🎂 🎄 )))
+(power-set B)
+    → { ∅ { 🍇 } { 🍇 🍎 } { 🍇 🍎 🎂 } { 🍇 🍎 🎂 🎄 } { 🍇 🍎 🎄 } { 🍇 🎂 } { 🍇 🎂 🎄 }
+      { 🍇 🎄 } { 🍎 } { 🍎 🎂 } { 🍎 🎂 🎄 } { 🍎 🎄 } { 🎂 } { 🎂 🎄 } { 🎄 } }
+
+;; The Von Neumann universe
+
+(define V0 (power-set null)) ;; null and ∅ are the same
+       → { ∅ }
+(define V1 (power-set V0))
+       → { ∅ { ∅ } }
+(define V2 (power-set V1))
+       → { ∅ { ∅ } { ∅ { ∅ } } { { ∅ } } }
+(define V3 (power-set V2))
+       → { ∅ { ∅ } { ∅ { ∅ } } …🔃 )
+(length V3) → 16
+(define V4 (power-set V3))
+(length V4)  → 65536
+;; length V5 = 2^65536 : out of bounds