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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 | * |
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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) | |
38 | * that %nil MUST be considered true | |
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 | /* | |
44 | * Use these macros if %nil will never be tested, | |
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 | */ | |
55 | #if SCM_ENABLE_ELISP | |
56 | # define scm_is_false_or_nil(x) \ | |
57 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_ELISP_NIL, SCM_BOOL_F)) | |
58 | #else | |
59 | # define scm_is_false_or_nil(x) (scm_is_false_assume_not_nil (x)) | |
60 | #endif | |
61 | #define scm_is_true_and_not_nil(x) (!scm_is_false_or_nil (x)) | |
0f2d19dd | 62 | |
d38b431a AW |
63 | /* %nil is false. */ |
64 | #define scm_is_false(x) (scm_is_false_or_nil (x)) | |
45f4cbdf MW |
65 | #define scm_is_true(x) (!scm_is_false (x)) |
66 | ||
67 | /* | |
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. | |
74 | * | |
75 | * See the comments preceeding the definitions of SCM_BOOL_F and | |
76 | * SCM_MATCHES_BITS_IN_COMMON in tags.h for more information. | |
77 | * | |
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, | |
f60c2c4e | 80 | * SCM_BOOL_T, SCM_ELISP_NIL, or SCM_XXX_ANOTHER_BOOLEAN_DONT_USE_0. |
45f4cbdf MW |
81 | * Otherwise, it returns 0. |
82 | */ | |
83 | #if SCM_ENABLE_ELISP | |
84 | # define scm_is_bool_or_nil(x) \ | |
85 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_T, SCM_ELISP_NIL)) | |
86 | #else | |
87 | # define scm_is_bool_or_nil(x) (scm_is_bool_and_not_nil (x)) | |
88 | #endif | |
89 | ||
90 | #define scm_is_bool_and_not_nil(x) \ | |
91 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_BOOL_T)) | |
92 | ||
baedef98 LC |
93 | SCM_API int scm_is_bool (SCM); |
94 | ||
d38b431a | 95 | #define scm_is_bool(x) (scm_is_bool_or_nil (x)) |
3a684cc6 | 96 | |
ede310d8 | 97 | #define scm_from_bool(x) ((x) ? SCM_BOOL_T : SCM_BOOL_F) |
3a684cc6 MV |
98 | SCM_API int scm_to_bool (SCM x); |
99 | ||
0f2d19dd JB |
100 | \f |
101 | ||
45f4cbdf MW |
102 | /* |
103 | * The following macros efficiently implement boolean truth testing as | |
104 | * expected by most lisps, which treat '() aka SCM_EOL as false. | |
105 | * | |
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. | |
112 | * | |
113 | * See the comments preceeding the definitions of SCM_BOOL_F and | |
114 | * SCM_MATCHES_BITS_IN_COMMON in tags.h for more information. | |
115 | * | |
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. | |
119 | */ | |
120 | #if SCM_ENABLE_ELISP | |
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)) | |
124 | #endif | |
125 | ||
126 | \f | |
127 | ||
e4e93373 MV |
128 | SCM_API SCM scm_not (SCM x); |
129 | SCM_API SCM scm_boolean_p (SCM obj); | |
3a684cc6 | 130 | |
102dbb6f | 131 | SCM_INTERNAL void scm_init_boolean (void); |
0f2d19dd | 132 | |
0527e687 | 133 | #endif /* SCM_BOOLEAN_H */ |
89e00824 ML |
134 | |
135 | /* | |
136 | Local Variables: | |
137 | c-file-style: "gnu" | |
138 | End: | |
139 | */ |