From 1daa266dd0a6381c58eba950dd935686dadee166 Mon Sep 17 00:00:00 2001 From: Mark H Weaver Date: Fri, 18 Apr 2014 15:04:12 -0400 Subject: [PATCH] SRFI-1 'length+' raises an error unless passed a proper or circular list. * libguile/srfi-1.c (scm_srfi1_length_plus): Rewrite to raise an error unless passed a proper or circular list, based on code from 'scm_ilength'. * test-suite/tests/srfi-1.test (length+): Add tests. --- libguile/srfi-1.c | 30 +++++++++++++++++++++++++++--- test-suite/tests/srfi-1.test | 7 ++++++- 2 files changed, 33 insertions(+), 4 deletions(-) diff --git a/libguile/srfi-1.c b/libguile/srfi-1.c index 54c7e2a..a7ffeec 100644 --- a/libguile/srfi-1.c +++ b/libguile/srfi-1.c @@ -1,7 +1,7 @@ /* srfi-1.c --- SRFI-1 procedures for Guile * * Copyright (C) 1995, 1996, 1997, 2000, 2001, 2002, 2003, 2005, 2006, - * 2008, 2009, 2010, 2011 Free Software Foundation, Inc. + * 2008, 2009, 2010, 2011, 2014 Free Software Foundation, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License @@ -614,8 +614,32 @@ SCM_DEFINE (scm_srfi1_length_plus, "length+", 1, 0, 0, "circular.") #define FUNC_NAME s_scm_srfi1_length_plus { - long len = scm_ilength (lst); - return (len >= 0 ? SCM_I_MAKINUM (len) : SCM_BOOL_F); + size_t i = 0; + SCM tortoise = lst; + SCM hare = lst; + + do + { + if (SCM_NULL_OR_NIL_P (hare)) + return scm_from_size_t (i); + if (!scm_is_pair (hare)) + scm_wrong_type_arg_msg (FUNC_NAME, 1, lst, "proper or circular list"); + hare = SCM_CDR (hare); + i++; + if (SCM_NULL_OR_NIL_P (hare)) + return scm_from_size_t (i); + if (!scm_is_pair (hare)) + scm_wrong_type_arg_msg (FUNC_NAME, 1, lst, "proper or circular list"); + hare = SCM_CDR (hare); + i++; + /* For every two steps the hare takes, the tortoise takes one. */ + tortoise = SCM_CDR(tortoise); + } + while (!scm_is_eq (hare, tortoise)); + + /* If the tortoise ever catches the hare, then the list must contain + a cycle. */ + return SCM_BOOL_F; } #undef FUNC_NAME diff --git a/test-suite/tests/srfi-1.test b/test-suite/tests/srfi-1.test index d40f8e1..9a2ed94 100644 --- a/test-suite/tests/srfi-1.test +++ b/test-suite/tests/srfi-1.test @@ -1,6 +1,7 @@ ;;;; srfi-1.test --- Test suite for Guile's SRFI-1 functions. -*- scheme -*- ;;;; -;;;; Copyright 2003, 2004, 2005, 2006, 2008, 2009, 2010, 2011 Free Software Foundation, Inc. +;;;; Copyright 2003, 2004, 2005, 2006, 2008, 2009, 2010, 2011, +;;;; 2014 Free Software Foundation, Inc. ;;;; ;;;; This library is free software; you can redistribute it and/or ;;;; modify it under the terms of the GNU Lesser General Public @@ -1329,6 +1330,10 @@ (length+)) (pass-if-exception "too many args" exception:wrong-num-args (length+ 123 456)) + (pass-if-exception "not a pair" exception:wrong-type-arg + (length+ 'x)) + (pass-if-exception "improper list" exception:wrong-type-arg + (length+ '(x y . z))) (pass-if (= 0 (length+ '()))) (pass-if (= 1 (length+ '(x)))) (pass-if (= 2 (length+ '(x y)))) -- 1.8.4