Data update

Task/Modular-inverse/Ada/modular-inverse.adb

@@ -0,0 +1,19 @@
+with Ada.Text_IO;use Ada.Text_IO;
+procedure modular_inverse is
+  -- inv_mod calculates the inverse of a mod n. We should have n>0 and, at the end, the contract is a*Result=1 mod n
+  -- If this is false then we raise an exception (don't forget the -gnata option when you compile
+  function inv_mod (a : Integer; n : Positive) return Integer with post=> (a * inv_mod'Result) mod n = 1 is
+    -- To calculate the inverse we do as if we would calculate the GCD with the Euclid extended algorithm
+    -- (but we just keep the coefficient on a)
+    function inverse (a, b, u, v : Integer) return Integer is
+     (if b=0 then u else inverse (b, a mod b, v, u-(v*a)/b));
+  begin
+    return inverse (a, n, 1, 0);
+  end inv_mod;
+begin
+  -- This will output -48 (which is correct)
+  Put_Line (inv_mod (42,2017)'img);
+  -- The further line will raise an exception since the GCD will not be 1
+  Put_Line (inv_mod (42,77)'img);
+  exception when others => Put_Line ("The inverse doesn't exist.");
+end modular_inverse;

Task/Modular-inverse/PowerShell/modular-inverse.ps1

@@ -0,0 +1,23 @@
+function invmod($a,$n){
+        if ([int]$n -lt 0) {$n = -$n}
+        if ([int]$a -lt 0) {$a = $n - ((-$a) % $n)}
+
+	$t = 0
+	$nt = 1
+	$r = $n
+	$nr = $a % $n
+	while ($nr -ne 0) {
+		$q = [Math]::truncate($r/$nr)
+		$tmp = $nt
+		$nt = $t - $q*$nt
+		$t = $tmp
+		$tmp = $nr
+		$nr = $r - $q*$nr
+		$r = $tmp
+	}
+	if ($r -gt 1) {return -1}
+	if ($t -lt 0) {$t += $n}
+	return $t
+}
+
+invmod 42 2017

Task/Modular-inverse/Uiua/modular-inverse.uiua

@@ -0,0 +1,3 @@
+# Definition from https://github.com/Omnikar/uiua-math
+ModInv ← ˜⨂1˜◿×◡⋅⇡
+ModInv 42 2017