Data commit

Task/Miller-Rabin-primality-test/Icon/miller-rabin-primality-test.icon

@@ -0,0 +1,33 @@
+procedure main(A)
+   every n := !A do write(n," is ",(mrp(n,5),"probably prime")|"composite")
+end
+
+procedure mrp(n, k)
+    if n = 2 then return ""
+    if n%2 = 0 then fail
+    nm1 := decompose(n-1)
+    s := nm1[1]
+    d := nm1[2]
+    every !k do {
+        a := ?(n-2)+1
+        x := (a^d)%n
+        if x = (1|(n-1)) then next
+        every !(s-1) do {
+            x := (x*x)%n
+            if x = 1 then fail
+            if x = (n-1) then break next
+            }
+        fail
+        }
+    return ""
+end
+
+procedure decompose(nm1)
+    s := 1
+    d := nm1
+    while d%2 = 0 do {
+        d /:= 2
+        s +:= 1
+        }
+    return [s,d]
+end