kc3-lang/kc3

diff --git a/libc3/ratio.c b/libc3/ratio.c
index 2e6e3d4..6130e48 100644
--- a/libc3/ratio.c
+++ b/libc3/ratio.c
@@ -127,6 +127,22 @@ s_ratio * ratio_add (const s_ratio *a, const s_ratio *b,
   return dest;
 }
 
+s_ratio * ratio_neg (const s_ratio *r, s_ratio *dest)
+{
+  s_ratio tmp = {0};
+  assert(r);
+  assert(dest);
+  assert(! integer_is_zero(&r->denominator));
+  if (! integer_neg(&r->numerator, &tmp.numerator))
+    return NULL;
+  if (! integer_init_copy(&tmp.denominator, &r->denominator)) {
+    integer_clean(&tmp.numerator);
+    return NULL;
+  }
+  *dest = tmp;
+  return dest;
+}
+
 s_ratio * ratio_sub (const s_ratio *a, const s_ratio *b,
                            s_ratio *dest)
 {
@@ -314,4 +330,4 @@ u8 ratio_to_u8 (const s_ratio *r)
   u8 denominator = integer_to_u8(&r->denominator);
 
   return numerator / denominator;
-}
\ No newline at end of file
+}
diff --git a/libc3/ratio.h b/libc3/ratio.h
index 75f616d..6559e58 100644
--- a/libc3/ratio.h
+++ b/libc3/ratio.h
@@ -51,11 +51,12 @@ u8      ratio_to_u8 (const s_ratio *r);
 /* Operators. */
 s_ratio * ratio_add (const s_ratio *a, const s_ratio *b,
                      s_ratio *dest);
-s_ratio * ratio_sub (const s_ratio *a, const s_ratio *b,
+s_ratio * ratio_div (const s_ratio *a, const s_ratio *b,
                      s_ratio *dest);
 s_ratio * ratio_mul (const s_ratio *a, const s_ratio *b,
                      s_ratio *dest);
-s_ratio * ratio_div (const s_ratio *a, const s_ratio *b,
+s_ratio * ratio_neg (const s_ratio *r, s_ratio *dest);
+s_ratio * ratio_sub (const s_ratio *a, const s_ratio *b,
                      s_ratio *dest);
 
 /* Setters. */
diff --git a/libc3/tag.c b/libc3/tag.c
index ac5f1bc..dfc996f 100644
--- a/libc3/tag.c
+++ b/libc3/tag.c
@@ -599,6 +599,10 @@ s_tag * tag_neg (const s_tag *tag, s_tag *result)
     result->type = TAG_INTEGER;
     integer_neg(&tag->data.integer, &result->data.integer);
     return result;
+  case TAG_RATIO:
+    result->type = TAG_RATIO;
+    ratio_neg(&tag->data.ratio, &result->data.ratio);
+    return result;
   case TAG_SW:
     if (tag->data.sw == SW_MIN) {
       integer_init_sw(&tmp, tag->data.sw);