007500e10a428b9937d72c3cee6e48d6f9112232
6 /* Copyright (C) 1995,1996,2000, 2006, 2008, 2009, 2010 Free Software Foundation, Inc.
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public License
10 * as published by the Free Software Foundation; either version 3 of
11 * the License, or (at your option) any later version.
13 * This library is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
26 #include "libguile/__scm.h"
30 /* Boolean Values. Obviously there are #t and #f, but there is also nil to deal
31 * with. We choose to treat nil as a false boolean. All options might silently
32 * break existing code, but this one seems most responsible.
37 * Use these macros if it's important (for correctness)
38 * that %nil MUST be considered true
40 #define scm_is_false_and_not_nil(x) (scm_is_eq ((x), SCM_BOOL_F))
41 #define scm_is_true_or_nil(x) (!scm_is_eq ((x), SCM_BOOL_F))
44 * Use these macros if %nil will never be tested,
45 * for increased efficiency.
47 #define scm_is_false_assume_not_nil(x) (scm_is_eq ((x), SCM_BOOL_F))
48 #define scm_is_true_assume_not_nil(x) (!scm_is_eq ((x), SCM_BOOL_F))
51 * See the comments preceeding the definitions of SCM_BOOL_F and
52 * SCM_MATCHES_BITS_IN_COMMON in tags.h for more information on
53 * how the following macro works.
56 # define scm_is_false_or_nil(x) \
57 (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_ELISP_NIL, SCM_BOOL_F))
59 # define scm_is_false_or_nil(x) (scm_is_false_assume_not_nil (x))
61 #define scm_is_true_and_not_nil(x) (!scm_is_false_or_nil (x))
64 #define scm_is_false(x) (scm_is_false_or_nil (x))
65 #define scm_is_true(x) (!scm_is_false (x))
68 * Since we know SCM_BOOL_F and SCM_BOOL_T differ by exactly one bit,
69 * and that SCM_BOOL_F and SCM_ELISP_NIL differ by exactly one bit,
70 * and that they of course can't be the same bit (or else SCM_BOOL_T
71 * and SCM_ELISP_NIL be would equal), it follows that SCM_BOOL_T and
72 * SCM_ELISP_NIL differ by exactly two bits, and these are the bits
73 * which will be ignored by SCM_MATCHES_BITS_IN_COMMON below.
75 * See the comments preceeding the definitions of SCM_BOOL_F and
76 * SCM_MATCHES_BITS_IN_COMMON in tags.h for more information.
78 * If SCM_ENABLE_ELISP is true, then scm_is_bool_or_nil(x)
79 * returns 1 if and only if x is one of the following: SCM_BOOL_F,
80 * SCM_BOOL_T, SCM_ELISP_NIL, or SCM_XXX_ANOTHER_BOOLEAN_DONT_USE_0.
81 * Otherwise, it returns 0.
84 # define scm_is_bool_or_nil(x) \
85 (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_T, SCM_ELISP_NIL))
87 # define scm_is_bool_or_nil(x) (scm_is_bool_and_not_nil (x))
90 #define scm_is_bool_and_not_nil(x) \
91 (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_BOOL_T))
93 SCM_API
int scm_is_bool (SCM
);
95 #define scm_is_bool(x) (scm_is_bool_or_nil (x))
97 #define scm_from_bool(x) ((x) ? SCM_BOOL_T : SCM_BOOL_F)
98 SCM_API
int scm_to_bool (SCM x
);
103 * The following macros efficiently implement boolean truth testing as
104 * expected by most lisps, which treat '() aka SCM_EOL as false.
106 * Since we know SCM_ELISP_NIL and SCM_BOOL_F differ by exactly one
107 * bit, and that SCM_ELISP_NIL and SCM_EOL differ by exactly one bit,
108 * and that they of course can't be the same bit (or else SCM_BOOL_F
109 * and SCM_EOL be would equal), it follows that SCM_BOOL_F and SCM_EOL
110 * differ by exactly two bits, and these are the bits which will be
111 * ignored by SCM_MATCHES_BITS_IN_COMMON below.
113 * See the comments preceeding the definitions of SCM_BOOL_F and
114 * SCM_MATCHES_BITS_IN_COMMON in tags.h for more information.
116 * scm_is_lisp_false(x) returns 1 if and only if x is one of the
117 * following: SCM_BOOL_F, SCM_ELISP_NIL, SCM_EOL or
118 * SCM_XXX_ANOTHER_LISP_FALSE_DONT_USE. Otherwise, it returns 0.
121 # define scm_is_lisp_false(x) \
122 (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_EOL))
123 # define scm_is_lisp_true(x) (!scm_is_lisp_false(x))
128 SCM_API SCM
scm_not (SCM x
);
129 SCM_API SCM
scm_boolean_p (SCM obj
);
131 SCM_INTERNAL
void scm_init_boolean (void);
133 #endif /* SCM_BOOLEAN_H */