initial

silly.c

@@ -0,0 +1,67 @@
+#include "silly.h"
+
+silly silly_zeros() {
+  silly s;
+  s.sign = 0;
+  s.before = 0;
+  s.after = 0;
+  return s;
+}
+
+silly silly_add(silly x, silly y) {
+  if (x.sign ^ y.sign) {
+    if (x.sign) {
+      x.sign = 0;
+      return silly_sub(y, x);
+    }
+    y.sign = 0;
+    return silly_sub(x, y);
+  }
+  silly z = silly_zeros();
+
+  z.sign = x.sign | y.sign;
+  // Note: Overflow
+  z.before = x.before + y.before;
+  z.after = x.after + y.after;
+
+  if (z.after < x.after && z.after < y.after) z.before += 1;
+  return z;
+}
+
+silly silly_sub(silly x, silly y) {
+  if (y.sign) {
+    y.sign = 0;
+    return silly_add(x, y);
+  }
+
+  if (x.sign) {
+    x.sign = 0;
+    x = silly_add(x, y);
+    x.sign = 1;
+    return x;
+  }
+
+  silly z = silly_zeros();
+
+  // Note: Underflow
+  z.before = x.before - y.before;
+
+  if (z.before > x.before) {
+    z.sign = 1;
+    z.before = 0xffffffff - z.before + 1;
+  }
+
+  z.after = x.after - y.after;
+
+  if (z.after > x.after) z.before -= 1;
+
+  return z;
+}
+
+char* silly_to_string(silly s) {
+  char* res = malloc(23);
+
+  snprintf(res, 23, "%s%010d.%010d", s.sign? "-" : "+", s.before, s.after);
+
+  return res;
+}