summaryrefslogtreecommitdiff
path: root/libguile/list.c
diff options
context:
space:
mode:
Diffstat (limited to 'libguile/list.c')
-rw-r--r--libguile/list.c59
1 files changed, 51 insertions, 8 deletions
diff --git a/libguile/list.c b/libguile/list.c
index 23ef40407..704151519 100644
--- a/libguile/list.c
+++ b/libguile/list.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1995,1996,1997,2000,2001,2003,2004,2008,2009,2010
+/* Copyright (C) 1995,1996,1997,2000,2001,2003,2004,2008,2009,2010,2011
* Free Software Foundation, Inc.
*
* This library is free software; you can redistribute it and/or
@@ -617,8 +617,32 @@ SCM_DEFINE (scm_memq, "memq", 2, 0, 0,
"returned.")
#define FUNC_NAME s_scm_memq
{
- SCM_VALIDATE_LIST (2, lst);
- return scm_c_memq (x, lst);
+ SCM hare = lst, tortoise = lst;
+
+ while (scm_is_pair (hare))
+ {
+ if (scm_is_eq (SCM_CAR (hare), x))
+ return hare;
+ else
+ hare = SCM_CDR (hare);
+
+ if (!scm_is_pair (hare))
+ break;
+
+ if (scm_is_eq (SCM_CAR (hare), x))
+ return hare;
+ else
+ hare = SCM_CDR (hare);
+
+ tortoise = SCM_CDR (tortoise);
+ if (SCM_UNLIKELY (scm_is_eq (hare, tortoise)))
+ break;
+ }
+
+ if (SCM_LIKELY (scm_is_null (hare)))
+ return SCM_BOOL_F;
+ else
+ scm_wrong_type_arg_msg (FUNC_NAME, 2, lst, "list");
}
#undef FUNC_NAME
@@ -633,13 +657,32 @@ SCM_DEFINE (scm_memv, "memv", 2, 0, 0,
"returned.")
#define FUNC_NAME s_scm_memv
{
- SCM_VALIDATE_LIST (2, lst);
- for (; !SCM_NULL_OR_NIL_P (lst); lst = SCM_CDR (lst))
+ SCM hare = lst, tortoise = lst;
+
+ while (scm_is_pair (hare))
{
- if (! scm_is_false (scm_eqv_p (SCM_CAR (lst), x)))
- return lst;
+ if (scm_is_true (scm_eqv_p (SCM_CAR (hare), x)))
+ return hare;
+ else
+ hare = SCM_CDR (hare);
+
+ if (!scm_is_pair (hare))
+ break;
+
+ if (scm_is_true (scm_eqv_p (SCM_CAR (hare), x)))
+ return hare;
+ else
+ hare = SCM_CDR (hare);
+
+ tortoise = SCM_CDR (tortoise);
+ if (SCM_UNLIKELY (scm_is_eq (hare, tortoise)))
+ break;
}
- return SCM_BOOL_F;
+
+ if (SCM_LIKELY (scm_is_null (hare)))
+ return SCM_BOOL_F;
+ else
+ scm_wrong_type_arg_msg (FUNC_NAME, 2, lst, "list");
}
#undef FUNC_NAME