jet: +find

pkg/urbit/include/jets/w.h

@@ -20,6 +20,7 @@
     u3_noun u3wb_bind(u3_noun);
     u3_noun u3wb_clap(u3_noun);
     u3_noun u3wb_drop(u3_noun);
+    u3_noun u3wb_find(u3_noun);
     u3_noun u3wb_flop(u3_noun);
     u3_noun u3wb_lent(u3_noun);
     u3_noun u3wb_levy(u3_noun);

pkg/urbit/jets/b/find.c

@@ -0,0 +1,47 @@
+/* j/2/find.c
+**
+*/
+#include "all.h"
+
+
+/* functions
+*/
+u3_noun
+u3qb_find(u3_noun nedl, u3_noun hstk)
+{
+  c3_w i = 0;
+
+  while ( 1 ) {
+    if ( u3_nul == nedl) {
+      return u3_nul;
+    } else if ( u3_nul == hstk ) {
+      return u3_nul;
+    }
+
+    u3_noun n = nedl;
+    u3_noun h = hstk;
+    while (c3y == u3r_sing(u3h(n), u3h(h))) {
+      if ( u3_nul == u3t(n) ) {
+        return u3nc(0, i);
+      }
+
+      n = u3t(n);
+      h = u3t(h);
+    }
+
+    i = u3i_vint(i);
+    hstk = u3t(hstk);
+  }
+}
+
+u3_noun
+u3wb_find(u3_noun cor)
+{
+  u3_noun a, b;
+
+  if ( c3n == u3r_mean(cor, u3x_sam_2, &a, u3x_sam_3, &b, 0) ) {
+    return u3m_bail(c3__exit);
+  } else {
+    return u3qb_find(a, b);
+  }
+}

pkg/urbit/jets/tree.c

@@ -1286,6 +1286,8 @@ static c3_c* _141_tri_ha[] = {
 
 /* layer two
 */
+static u3j_harm _141_two_find_a[] = {{".2", u3wb_find, c3y}, {}};
+
 static u3j_harm _141_two_flop_a[] = {{".2", u3wb_flop, c3y}, {}};
 static c3_c* _141_two_flop_ha[] = {
   "73ac3be0119bcb822621de738f90975d98ce1ff3fb9a52853adc638271f61cd2",
@@ -1714,6 +1716,7 @@ static c3_c* _141_two_rub_ha[] = {
 static u3j_core _141_two_d[] =
 { { "tri",  3, 0, _141_tri_d, _141_tri_ha },
 
+  { "find", 7, _141_two_find_a },
   { "flop", 7, _141_two_flop_a, 0, _141_two_flop_ha },
   { "lent", 7, _141_two_lent_a, 0, _141_two_lent_ha },
   { "levy", 7, _141_two_levy_a, 0, _141_two_levy_ha },