Data commit

Task/Church-numerals/Go/church-numerals.go

@@ -0,0 +1,78 @@
+package main
+
+import "fmt"
+
+type any = interface{}
+
+type fn func(any) any
+
+type church func(fn) fn
+
+func zero(f fn) fn {
+    return func(x any) any {
+        return x
+    }
+}
+
+func (c church) succ() church {
+    return func(f fn) fn {
+        return func(x any) any {
+            return f(c(f)(x))
+        }
+    }
+}
+
+func (c church) add(d church) church {
+    return func(f fn) fn {
+        return func(x any) any {
+            return c(f)(d(f)(x))
+        }
+    }
+}
+
+func (c church) mul(d church) church {
+    return func(f fn) fn {
+        return func(x any) any {
+            return c(d(f))(x)
+        }
+    }
+}
+
+func (c church) pow(d church) church {
+    di := d.toInt()
+    prod := c
+    for i := 1; i < di; i++ {
+        prod = prod.mul(c)
+    }
+    return prod
+}
+
+func (c church) toInt() int {
+    return c(incr)(0).(int)
+}
+
+func intToChurch(i int) church {
+    if i == 0 {
+        return zero
+    } else {
+        return intToChurch(i - 1).succ()
+    }
+}
+
+func incr(i any) any {
+    return i.(int) + 1
+}
+
+func main() {
+    z := church(zero)
+    three := z.succ().succ().succ()
+    four := three.succ()
+
+    fmt.Println("three        ->", three.toInt())
+    fmt.Println("four         ->", four.toInt())
+    fmt.Println("three + four ->", three.add(four).toInt())
+    fmt.Println("three * four ->", three.mul(four).toInt())
+    fmt.Println("three ^ four ->", three.pow(four).toInt())
+    fmt.Println("four ^ three ->", four.pow(three).toInt())
+    fmt.Println("5 -> five    ->", intToChurch(5).toInt())
+}