From 2b4dff1bc2c3274201cdda958037b9065ca974bf Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Wed, 27 Dec 2023 15:45:25 -0800
Subject: rperm: change state representation to vector.

* combi.c (rperm_init): New static function.
(rperm_while_fun, rperm_gen_fun): Retrieve state
info from vector-based state rather than cons.
(rperm_list, rperm_vec, rperm_str): Call rperm_init to
allocate state.
---
 combi.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/combi.c b/combi.c
index 79787f04..c674686d 100644
--- a/combi.c
+++ b/combi.c
@@ -262,16 +262,26 @@ val perm(val seq, val k)
   }
 }
 
+static val rperm_init(val list, val k)
+{
+  val vec = vector(k, list);
+  val env = vector(two, nil);
+  set(vecref_l(env, zero), list);
+  set(vecref_l(env, one), vec);
+  return env;
+}
+
 static val rperm_while_fun(val env)
 {
-  val vec = cdr(env);
+  val vec = env->v.vec[1];
   return consp(vecref(vec, zero));
 }
 
 static val rperm_gen_fun(val env)
 {
   val self = lit("rperm");
-  cons_bind (list, vec, env);
+  val list = env->v.vec[0];
+  val vec = env->v.vec[1];
   list_collect_decl(out, ptail);
   cnum i;
   cnum len = c_num(length_vec(vec), self);
@@ -292,8 +302,7 @@ static val rperm_gen_fun(val env)
 
 static val rperm_list(val list, val k)
 {
-  val vec = vector(k, list);
-  val env = cons(list, vec);
+  val env = rperm_init(list, k);
   return generate(func_f0(env, rperm_while_fun),
                   func_f0(env, rperm_gen_fun));
 }
@@ -307,8 +316,7 @@ static val rperm_vec_gen_fun(val env)
 static val rperm_vec(val ve, val k)
 {
   val list = list_vec(ve);
-  val vec = vector(k, list);
-  val env = cons(list, vec);
+  val env = rperm_init(list, k);
   return generate(func_f0(env, rperm_while_fun),
                   func_f0(env, rperm_vec_gen_fun));
 }
@@ -322,8 +330,7 @@ static val rperm_str_gen_fun(val env)
 static val rperm_str(val str, val k)
 {
   val list = list_str(str);
-  val vec = vector(k, list);
-  val env = cons(list, vec);
+  val env = rperm_init(list, k);
   return generate(func_f0(env, rperm_while_fun),
                   func_f0(env, rperm_str_gen_fun));
 }
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