Data commit

Task/Church-numerals/Groovy/church-numerals.groovy

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+class ChurchNumerals {
+    static void main(args) {
+
+        def zero = { f -> { a -> a } }
+        def succ = { n -> { f -> { a -> f(n(f)(a)) } } }
+        def add = { n -> { k -> { n(succ)(k) } } }
+        def mult = { f -> { g -> { a -> f(g(a)) } } }
+        def pow = { f -> { g -> g(f) } }
+
+        def toChurchNum
+        toChurchNum = { n ->
+            n == 0 ? zero : succ(toChurchNum(n - 1))
+        }
+
+        def toInt = { n ->
+            n(x -> x + 1)(0)
+        }
+
+        def three = succ(succ(succ(zero)))
+        println toInt(three) // prints 3
+
+        def four = succ(three)
+        println toInt(four) // prints 4
+
+        println "3 + 4 = ${toInt(add(three)(four))}" // prints 3 + 4 = 7
+        println "4 + 3 = ${toInt(add(four)(three))}" // prints 4 + 3 = 7
+
+        println "3 * 4 = ${toInt(mult(three)(four))}" // prints 3 * 4 = 12
+        println "4 * 3 = ${toInt(mult(four)(three))}" // prints 4 * 3 = 12
+
+        println "3 ^ 4 = ${toInt(pow(three)(four))}" // prints 3 ^ 4 = 81
+        println "4 ^ 3 = ${toInt(pow(four)(three))}" // prints 4 ^ 3 = 64
+    }
+}