diff options
Diffstat (limited to 'libguile/pairs.h')
| -rw-r--r-- | libguile/pairs.h | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/libguile/pairs.h b/libguile/pairs.h index a6d44d289..47bb187ff 100644 --- a/libguile/pairs.h +++ b/libguile/pairs.h @@ -3,7 +3,7 @@ #ifndef SCM_PAIRS_H #define SCM_PAIRS_H -/* Copyright (C) 1995,1996,2000,2001, 2004, 2006, 2008 Free Software Foundation, Inc. +/* Copyright (C) 1995,1996,2000,2001, 2004, 2006, 2008, 2009 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 @@ -34,7 +34,32 @@ # define SCM_VALIDATE_PAIR(cell, expr) (expr) #endif -#define scm_is_null(x) (scm_is_eq ((x), SCM_EOL)) +/* + * Use scm_is_null_and_not_nil if it's important (for correctness) + * that %nil must NOT be considered null. + */ +#define scm_is_null_and_not_nil(x) (scm_is_eq ((x), SCM_EOL)) + +/* + * Use scm_is_null_assume_not_nil if %nil will never be tested, + * for increased efficiency. + */ +#define scm_is_null_assume_not_nil(x) (scm_is_eq ((x), SCM_EOL)) + +/* + * See the comments preceeding the definitions of SCM_BOOL_F and + * SCM_MATCHES_BITS_IN_COMMON in tags.h for more information on + * how the following macro works. + */ +#if SCM_ENABLE_ELISP +# define scm_is_null_or_nil(x) \ + (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_ELISP_NIL, SCM_EOL)) +#else +# define scm_is_null_or_nil(x) (scm_is_null_assume_not_nil (x)) +#endif + +/* XXX Should scm_is_null treat %nil as null by default? */ +#define scm_is_null(x) (scm_is_null_and_not_nil(x)) #define SCM_CAR(x) (SCM_VALIDATE_PAIR (x, SCM_CELL_OBJECT_0 (x))) #define SCM_CDR(x) (SCM_VALIDATE_PAIR (x, SCM_CELL_OBJECT_1 (x))) |