Data commit

Task/Modular-inverse/Cowgol/modular-inverse.cowgol

@@ -0,0 +1,46 @@
+include "cowgol.coh";
+
+sub mulinv(a: int32, b: int32): (t: int32) is
+    if b<0 then b := -b; end if;
+    if a<0 then a := b - (-a % b); end if;
+    t := 0;
+    var nt: int32 := 1;
+    var r := b;
+    var nr := a % b;
+    while nr != 0 loop
+        var q := r / nr;
+        var tmp := nt; nt := t - q*nt; t := tmp;
+        tmp := nr; nr := r - q*nr; r := tmp;
+    end loop;
+    if r>1 then t := -1;
+    elseif t<0 then t := t + b;
+    end if;
+end sub;
+
+record Pair is
+    a: int32;
+    b: int32;
+end record;
+
+var data: Pair[] := {
+    {42, 2017},
+    {40, 1},
+    {52, -217},
+    {-486, 217},
+    {40, 2018}
+};
+
+var i: @indexof data := 0;
+while i < @sizeof data loop
+    print_i32(data[i].a as uint32);
+    print(", ");
+    print_i32(data[i].b as uint32);
+    print(" -> ");
+    var mi := mulinv(data[i].a, data[i].b);
+    if mi<0
+        then print("no inverse");
+        else print_i32(mi as uint32);
+    end if;
+    print_nl();
+    i := i + 1;
+end loop;