1 files changed, 66 insertions, 0 deletions
diff --git a/vere/pkg/noun/jets/c/peg.c b/vere/pkg/noun/jets/c/peg.c
new file mode 100644
index 0000000..a700752
--- /dev/null
+++ b/vere/pkg/noun/jets/c/peg.c
@@ -0,0 +1,66 @@
+#include "jets/q.h"
+#include "jets/w.h"
+
+#include "noun.h"
+
+u3_noun
+u3qc_peg(u3_atom a, u3_atom b)
+{
+  if ( (0 == a) || (0 == b) ) {
+    return u3m_bail(c3__exit);
+  }
+  else if ( 1 == b ) {
+    return u3k(a);
+  }
+
+  c3_d a_d, b_d;
+  c3_w c_w;
+
+  if ( (c3y == u3a_is_cat(a)) && (c3y == u3a_is_cat(b)) ) {
+    c_w = c3_bits_word(b) - 1;
+    a_d = a;
+    b_d = b;
+  }
+  else {
+    c3_w d_w = u3r_met(0, a);
+    c3_d e_d;
+
+    c_w = u3r_met(0, b) - 1;
+    e_d = (c3_d)c_w + d_w;
+
+    if ( 64 <= e_d ) {
+      u3i_slab sab_u;
+      u3i_slab_init(&sab_u, 0, e_d);
+
+      u3r_chop(0, 0, c_w,   0, sab_u.buf_w, b);
+      u3r_chop(0, 0, d_w, c_w, sab_u.buf_w, a);
+
+      return u3i_slab_moot(&sab_u);
+    }
+
+    a_d = u3r_chub(0, a);
+    b_d = u3r_chub(0, b);
+  }
+
+  b_d  &= ((c3_d)1 << c_w) - 1;
+  a_d <<= c_w;
+  a_d  ^= b_d;
+
+  return u3i_chub(a_d);
+}
+
+u3_noun
+u3wc_peg(u3_noun cor)
+{
+  u3_noun a, b;
+
+  if ( (c3n == u3r_mean(cor, u3x_sam_2, &a, u3x_sam_3, &b, 0)) ||
+       (c3n == u3ud(b)) ||
+       (c3n == u3ud(a) && b != 1) )
+  {
+    return u3m_bail(c3__exit);
+  }
+  else {
+    return u3qc_peg(a, b);
+  }
+}