From 7865cfe9b3f20a8e47117d1fc075f0e2ad7642ce Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Wed, 22 Jan 2014 20:57:14 +0900
Subject: [PATCH] add pic_append

---
 include/picrin/pair.h |  1 +
 src/pair.c            | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/picrin/pair.h b/include/picrin/pair.h
index 02599ff6..f2ba887e 100644
--- a/include/picrin/pair.h
+++ b/include/picrin/pair.h
@@ -19,6 +19,7 @@ pic_value pic_list_from_array(pic_state *, size_t, pic_value *);
 
 int pic_length(pic_state *, pic_value);
 pic_value pic_reverse(pic_state *, pic_value);
+pic_value pic_append(pic_state *, pic_value, pic_value);
 
 pic_value pic_assq(pic_state *, pic_value key, pic_value assoc);
 pic_value pic_assoc(pic_state *, pic_value key, pic_value assoc);
diff --git a/src/pair.c b/src/pair.c
index ee443f68..989af584 100644
--- a/src/pair.c
+++ b/src/pair.c
@@ -114,6 +114,23 @@ pic_reverse(pic_state *pic, pic_value list)
   return acc;
 }
 
+pic_value
+pic_append(pic_state *pic, pic_value xs, pic_value ys)
+{
+  int ai = pic_gc_arena_preserve(pic);
+
+  if (pic_nil_p(xs)) {
+    return ys;
+  }
+  else {
+    xs = pic_cons(pic, pic_car(pic, xs), pic_append(pic, pic_cdr(pic, xs), ys));
+  }
+
+  pic_gc_arena_restore(pic, ai);
+  pic_gc_protect(pic, xs);
+  return xs;
+}
+
 pic_value
 pic_assq(pic_state *pic, pic_value key, pic_value assoc)
 {