Data commit

Task/Ackermann-function/Picat/ackermann-function.picat

@@ -0,0 +1,38 @@
+go =>
+    foreach(M in 0..3)
+        println([m=M,[a(M,N) : N in 0..16]])
+    end,
+    nl,
+    printf("a2(4,1): %d\n", a2(4,1)),
+    nl,
+    time(check_larger(3,10000)),
+    nl,
+    time(check_larger(4,2)),
+    nl.
+
+% Using a2/2 and chop off large output
+check_larger(M,N) =>
+    printf("a2(%d,%d): ", M,N),
+    A = a2(M,N).to_string,
+    Len = A.len,
+    if Len < 50 then
+      println(A)
+    else
+      println(A[1..20] ++ ".." ++ A[Len-20..Len])
+    end,
+    println(digits=Len).
+
+% Plain tabled (memoized) version with guards
+table
+a(0, N) = N+1 => true.
+a(M, 0) = a(M-1,1), M > 0 => true.
+a(M, N) = a(M-1,a(M, N-1)), M > 0, N > 0 => true.
+
+% Faster and pure function version (no guards).
+% (Based on Python example.)
+table
+a2(0,N) = N + 1.
+a2(1,N) = N + 2.
+a2(2,N) = 2*N + 3.
+a2(3,N) = 8*(2**N - 1) + 5.
+a2(M,N) = cond(N == 0,a2(M-1, 1), a2(M-1, a2(M, N-1))).