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0f2d19dd JB |
1 | /* classes: h_files */ |
2 | ||
0527e687 DH |
3 | #ifndef SCM_BOOLEAN_H |
4 | #define SCM_BOOLEAN_H | |
5 | ||
baedef98 | 6 | /* Copyright (C) 1995,1996,2000, 2006, 2008, 2009, 2010 Free Software Foundation, Inc. |
0527e687 | 7 | * |
73be1d9e | 8 | * This library is free software; you can redistribute it and/or |
53befeb7 NJ |
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. | |
0527e687 | 12 | * |
53befeb7 NJ |
13 | * This library is distributed in the hope that it will be useful, but |
14 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
73be1d9e MV |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
16 | * Lesser General Public License for more details. | |
0527e687 | 17 | * |
73be1d9e MV |
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 | |
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20 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
21 | * 02110-1301 USA | |
73be1d9e | 22 | */ |
0527e687 | 23 | |
0f2d19dd | 24 | \f |
0527e687 | 25 | |
b4309c3c | 26 | #include "libguile/__scm.h" |
0f2d19dd JB |
27 | |
28 | \f | |
29 | ||
d38b431a AW |
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. | |
0f2d19dd JB |
33 | * |
34 | */ | |
0f2d19dd | 35 | |
45f4cbdf MW |
36 | /* |
37 | * Use these macros if it's important (for correctness) | |
92a61010 | 38 | * that #nil MUST be considered true |
45f4cbdf MW |
39 | */ |
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)) | |
42 | ||
43 | /* | |
92a61010 | 44 | * Use these macros if #nil will never be tested, |
45f4cbdf MW |
45 | * for increased efficiency. |
46 | */ | |
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)) | |
49 | ||
50 | /* | |
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. | |
54 | */ | |
c1b7c940 | 55 | #define scm_is_false_or_nil(x) \ |
45f4cbdf | 56 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_ELISP_NIL, SCM_BOOL_F)) |
45f4cbdf | 57 | #define scm_is_true_and_not_nil(x) (!scm_is_false_or_nil (x)) |
0f2d19dd | 58 | |
8a4ed2dd | 59 | /* #nil is false. */ |
d38b431a | 60 | #define scm_is_false(x) (scm_is_false_or_nil (x)) |
45f4cbdf MW |
61 | #define scm_is_true(x) (!scm_is_false (x)) |
62 | ||
63 | /* | |
64 | * Since we know SCM_BOOL_F and SCM_BOOL_T differ by exactly one bit, | |
65 | * and that SCM_BOOL_F and SCM_ELISP_NIL differ by exactly one bit, | |
66 | * and that they of course can't be the same bit (or else SCM_BOOL_T | |
67 | * and SCM_ELISP_NIL be would equal), it follows that SCM_BOOL_T and | |
68 | * SCM_ELISP_NIL differ by exactly two bits, and these are the bits | |
69 | * which will be ignored by SCM_MATCHES_BITS_IN_COMMON below. | |
70 | * | |
71 | * See the comments preceeding the definitions of SCM_BOOL_F and | |
72 | * SCM_MATCHES_BITS_IN_COMMON in tags.h for more information. | |
73 | * | |
74 | * If SCM_ENABLE_ELISP is true, then scm_is_bool_or_nil(x) | |
75 | * returns 1 if and only if x is one of the following: SCM_BOOL_F, | |
f60c2c4e | 76 | * SCM_BOOL_T, SCM_ELISP_NIL, or SCM_XXX_ANOTHER_BOOLEAN_DONT_USE_0. |
45f4cbdf MW |
77 | * Otherwise, it returns 0. |
78 | */ | |
c1b7c940 | 79 | #define scm_is_bool_or_nil(x) \ |
45f4cbdf | 80 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_T, SCM_ELISP_NIL)) |
45f4cbdf MW |
81 | #define scm_is_bool_and_not_nil(x) \ |
82 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_BOOL_T)) | |
83 | ||
baedef98 LC |
84 | SCM_API int scm_is_bool (SCM); |
85 | ||
d38b431a | 86 | #define scm_is_bool(x) (scm_is_bool_or_nil (x)) |
3a684cc6 | 87 | |
ede310d8 | 88 | #define scm_from_bool(x) ((x) ? SCM_BOOL_T : SCM_BOOL_F) |
3a684cc6 MV |
89 | SCM_API int scm_to_bool (SCM x); |
90 | ||
0f2d19dd JB |
91 | \f |
92 | ||
8a4ed2dd AW |
93 | /* Older spellings for the above routines, kept around for |
94 | compatibility. */ | |
95 | #define SCM_FALSEP(x) (scm_is_false (x)) | |
96 | #define SCM_NFALSEP(x) (scm_is_true (x)) | |
97 | #define SCM_BOOLP(x) (scm_is_bool (x)) | |
98 | #define SCM_BOOL(x) (scm_from_bool (x)) | |
99 | #define SCM_NEGATE_BOOL(f) (scm_from_bool (!(f))) | |
100 | #define SCM_BOOL_NOT(x) (scm_not (x)) | |
101 | ||
102 | \f | |
103 | ||
45f4cbdf MW |
104 | /* |
105 | * The following macros efficiently implement boolean truth testing as | |
106 | * expected by most lisps, which treat '() aka SCM_EOL as false. | |
107 | * | |
108 | * Since we know SCM_ELISP_NIL and SCM_BOOL_F differ by exactly one | |
109 | * bit, and that SCM_ELISP_NIL and SCM_EOL differ by exactly one bit, | |
110 | * and that they of course can't be the same bit (or else SCM_BOOL_F | |
111 | * and SCM_EOL be would equal), it follows that SCM_BOOL_F and SCM_EOL | |
112 | * differ by exactly two bits, and these are the bits which will be | |
113 | * ignored by SCM_MATCHES_BITS_IN_COMMON below. | |
114 | * | |
115 | * See the comments preceeding the definitions of SCM_BOOL_F and | |
116 | * SCM_MATCHES_BITS_IN_COMMON in tags.h for more information. | |
117 | * | |
118 | * scm_is_lisp_false(x) returns 1 if and only if x is one of the | |
119 | * following: SCM_BOOL_F, SCM_ELISP_NIL, SCM_EOL or | |
120 | * SCM_XXX_ANOTHER_LISP_FALSE_DONT_USE. Otherwise, it returns 0. | |
121 | */ | |
c1b7c940 | 122 | #define scm_is_lisp_false(x) \ |
45f4cbdf | 123 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_EOL)) |
45f4cbdf MW |
124 | |
125 | \f | |
126 | ||
e4e93373 MV |
127 | SCM_API SCM scm_not (SCM x); |
128 | SCM_API SCM scm_boolean_p (SCM obj); | |
3a684cc6 | 129 | |
102dbb6f | 130 | SCM_INTERNAL void scm_init_boolean (void); |
0f2d19dd | 131 | |
0527e687 | 132 | #endif /* SCM_BOOLEAN_H */ |
89e00824 ML |
133 | |
134 | /* | |
135 | Local Variables: | |
136 | c-file-style: "gnu" | |
137 | End: | |
138 | */ |