| 1 | /* classes: h_files */ |
| 2 | |
| 3 | #ifndef SCM_BOOLEAN_H |
| 4 | #define SCM_BOOLEAN_H |
| 5 | |
| 6 | /* Copyright (C) 1995,1996,2000, 2006, 2008, 2009, 2010, 2013 Free Software Foundation, Inc. |
| 7 | * |
| 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. |
| 12 | * |
| 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. |
| 17 | * |
| 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 |
| 21 | * 02110-1301 USA |
| 22 | */ |
| 23 | |
| 24 | \f |
| 25 | |
| 26 | #include "libguile/__scm.h" |
| 27 | |
| 28 | \f |
| 29 | |
| 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. |
| 33 | * |
| 34 | */ |
| 35 | |
| 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 | #define scm_is_false_or_nil(x) \ |
| 56 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_ELISP_NIL, SCM_BOOL_F)) |
| 57 | #define scm_is_true_and_not_nil(x) (!scm_is_false_or_nil (x)) |
| 58 | |
| 59 | /* #nil is false. */ |
| 60 | #define scm_is_false(x) (scm_is_false_or_nil (x)) |
| 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, |
| 76 | * SCM_BOOL_T, SCM_ELISP_NIL, or SCM_XXX_ANOTHER_BOOLEAN_DONT_USE_0. |
| 77 | * Otherwise, it returns 0. |
| 78 | */ |
| 79 | #define scm_is_bool_or_nil(x) \ |
| 80 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_T, SCM_ELISP_NIL)) |
| 81 | #define scm_is_bool_and_not_nil(x) \ |
| 82 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_BOOL_T)) |
| 83 | |
| 84 | SCM_API int scm_is_bool (SCM); |
| 85 | |
| 86 | #define scm_is_bool(x) (scm_is_bool_or_nil (x)) |
| 87 | |
| 88 | #define scm_from_bool(x) ((x) ? SCM_BOOL_T : SCM_BOOL_F) |
| 89 | SCM_API int scm_to_bool (SCM x); |
| 90 | |
| 91 | \f |
| 92 | |
| 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 | |
| 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 | */ |
| 122 | #define scm_is_lisp_false(x) \ |
| 123 | (SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_EOL)) |
| 124 | |
| 125 | \f |
| 126 | |
| 127 | SCM_API SCM scm_not (SCM x); |
| 128 | SCM_API SCM scm_boolean_p (SCM obj); |
| 129 | SCM_API SCM scm_nil_p (SCM obj); |
| 130 | |
| 131 | SCM_INTERNAL void scm_init_boolean (void); |
| 132 | |
| 133 | #endif /* SCM_BOOLEAN_H */ |
| 134 | |
| 135 | /* |
| 136 | Local Variables: |
| 137 | c-file-style: "gnu" |
| 138 | End: |
| 139 | */ |