32-way branching in intmap.scm, not 16-way
[bpt/guile.git] / libguile / boolean.h
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1/* classes: h_files */
2
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3#ifndef SCM_BOOLEAN_H
4#define SCM_BOOLEAN_H
5
84800dff 6/* Copyright (C) 1995,1996,2000, 2006, 2008, 2009, 2010, 2013 Free Software Foundation, Inc.
0527e687 7 *
73be1d9e 8 * This library is free software; you can redistribute it and/or
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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
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15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
0527e687 17 *
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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"
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27
28\f
29
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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.
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33 *
34 */
0f2d19dd 35
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36/*
37 * Use these macros if it's important (for correctness)
92a61010 38 * that #nil MUST be considered true
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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,
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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))
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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.
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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))
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81#define scm_is_bool_and_not_nil(x) \
82 (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_BOOL_T))
83
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84SCM_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)
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89SCM_API int scm_to_bool (SCM x);
90
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91\f
92
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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
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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))
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124
125\f
126
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127SCM_API SCM scm_not (SCM x);
128SCM_API SCM scm_boolean_p (SCM obj);
84800dff 129SCM_API SCM scm_nil_p (SCM obj);
3a684cc6 130
102dbb6f 131SCM_INTERNAL void scm_init_boolean (void);
0f2d19dd 132
0527e687 133#endif /* SCM_BOOLEAN_H */
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134
135/*
136 Local Variables:
137 c-file-style: "gnu"
138 End:
139*/