Data commit

Task/Modular-inverse/Seed7/modular-inverse.seed7

@@ -0,0 +1,43 @@
+const func bigInteger: modInverse (in var bigInteger: a,
+    in var bigInteger: b) is func
+  result
+    var bigInteger: modularInverse is 0_;
+  local
+    var bigInteger: b_bak is 0_;
+    var bigInteger: x is 0_;
+    var bigInteger: y is 1_;
+    var bigInteger: lastx is 1_;
+    var bigInteger: lasty is 0_;
+    var bigInteger: temp is 0_;
+    var bigInteger: quotient is 0_;
+  begin
+    if b < 0_ then
+      raise RANGE_ERROR;
+    end if;
+    if a < 0_ and b <> 0_ then
+      a := a mod b;
+    end if;
+    b_bak := b;
+    while b <> 0_ do
+      temp := b;
+      quotient := a div b;
+      b := a rem b;
+      a := temp;
+
+      temp := x;
+      x := lastx - quotient * x;
+      lastx := temp;
+
+      temp := y;
+      y := lasty - quotient * y;
+      lasty := temp;
+    end while;
+    if a = 1_ then
+      modularInverse := lastx;
+      if modularInverse < 0_ then
+        modularInverse +:= b_bak;
+      end if;
+    else
+      raise RANGE_ERROR;
+    end if;
+  end func;