1 files changed, 93 insertions, 0 deletions
diff --git a/vere/pkg/noun/jets/d/by_del.c b/vere/pkg/noun/jets/d/by_del.c
new file mode 100644
index 0000000..86ba416
--- /dev/null
+++ b/vere/pkg/noun/jets/d/by_del.c
@@ -0,0 +1,93 @@
+/// @file
+
+#include "jets/q.h"
+#include "jets/w.h"
+
+#include "noun.h"
+
+static u3_noun
+_rebalance(u3_noun a)
+{
+  u3_noun n_a, l_a, r_a;
+  u3x_trel(a, &n_a, &l_a, &r_a);
+
+  if ( u3_nul == l_a) {
+    return u3k(r_a);
+  }
+  else if ( u3_nul == r_a) {
+    return u3k(l_a);
+  }
+  else {
+    u3_noun n_l_a, l_l_a, r_l_a;
+    u3_noun n_r_a, l_r_a, r_r_a;
+    u3x_trel(l_a, &n_l_a, &l_l_a, &r_l_a);
+    u3x_trel(r_a, &n_r_a, &l_r_a, &r_r_a);
+
+    if ( c3y == u3qc_mor(u3h(n_l_a), u3h(n_r_a)) ) {
+      u3_noun new_right = u3nt(u3k(n_a),
+                               u3k(r_l_a),
+                               u3k(r_a));
+
+      u3_noun ret = u3nt(u3k(n_l_a),
+                         u3k(l_l_a),
+                         _rebalance(new_right));
+      u3z(new_right);
+
+      return ret;
+    }
+    else {
+      u3_noun new_left = u3nt(u3k(n_a),
+                              u3k(l_a),
+                              u3k(l_r_a));
+
+      u3_noun ret = u3nt(u3k(n_r_a),
+                         _rebalance(new_left),
+                         u3k(r_r_a));
+      u3z(new_left);
+
+      return ret;
+    }
+  }
+}
+
+u3_noun
+u3qdb_del(u3_noun a,
+          u3_noun b)
+{
+  if ( u3_nul == a ) {
+    return u3_nul;
+  }
+  else {
+    u3_noun n_a, lr_a;
+    u3_noun pn_a;
+    u3x_cell(a, &n_a, &lr_a);
+    u3x_cell(n_a, &pn_a, 0);
+
+    if ( c3y == u3r_sing(pn_a, b) ) {
+      return _rebalance(a);
+    }
+    else {
+      u3_noun l_a, r_a;
+      u3x_cell(lr_a, &l_a, &r_a);
+
+      if ( c3y == u3qc_gor(b, pn_a) ) {
+        return u3nt(u3k(n_a),
+                    u3qdb_del(l_a, b),
+                    u3k(r_a));
+      }
+      else {
+        return u3nt(u3k(n_a),
+                    u3k(l_a),
+                    u3qdb_del(r_a, b));
+      }
+    }
+  }
+}
+
+u3_noun
+u3wdb_del(u3_noun cor)
+{
+  u3_noun a, b;
+  u3x_mean(cor, u3x_sam, &b, u3x_con_sam, &a, 0);
+  return u3qdb_del(a, b);
+}