langs a-z

Task/Modular-inverse/OCaml/modular-inverse-1.ocaml

@@ -0,0 +1,8 @@
+let mul_inv a = function 1 -> 1 | b ->
+  let rec aux a b x0 x1 =
+    if a <= 1 then x1 else
+    if b = 0 then failwith "mul_inv" else
+    aux b (a mod b) (x1 - (a / b) * x0) x0
+  in
+  let x = aux a b 0 1 in
+  if x < 0 then x + b else x

Task/Modular-inverse/OCaml/modular-inverse-2.ocaml

@@ -0,0 +1,11 @@
+let rec gcd_ext a = function
+  | 0 -> (1, 0, a)
+  | b ->
+      let s, t, g = gcd_ext b (a mod b) in
+      (t, s - (a / b) * t, g)
+
+let mod_inv a m =
+  let mk_pos x = if x < 0 then x + m else x in
+  match gcd_ext a m with
+  | i, _, 1 -> mk_pos i
+  | _ -> failwith "mod_inv"

Task/Modular-inverse/Perl-6/modular-inverse.pl6

@@ -0,0 +1,11 @@
+sub inverse($n, :$modulo) {
+    my ($c, $d, $uc, $vc, $ud, $vd) = ($n % $modulo, $modulo, 1, 0, 0, 1);
+    my $q;
+    while $c != 0 {
+        ($q, $c, $d) = ($d div $c, $d % $c, $c);
+        ($uc, $vc, $ud, $vd) = ($ud - $q*$uc, $vd - $q*$vc, $uc, $vc);
+    }
+    return $ud < 0 ?? $ud + $modulo !! $ud;
+}
+
+say inverse 42, :modulo(2017)

Task/Modular-inverse/Run-BASIC/modular-inverse.run

@@ -0,0 +1,19 @@
+print multInv(42, 2017)
+end
+
+function multInv(a,b)
+	b0	= b
+	multInv	= 1
+	if b = 1 then goto [endFun]
+	while a > 1
+		q	= a / b
+		t	= b
+		b	= a mod b
+		a	= t
+		t	= x0
+		x0	= multInv - q * x0
+		multInv	= int(t)
+	wend
+	if multInv < 0 then multInv = multInv + b0
+[endFun]
+end function

Task/Modular-inverse/XPL0/modular-inverse.xpl0

@@ -0,0 +1,7 @@
+code IntOut=11, Text=12;
+int  X;
+def  A=42, M=2017;
+[for X:= 2 to M-1 do
+    if rem(A*X/M) = 1 then [IntOut(0, X);  exit];
+Text(0, "Does not exist");
+]