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#ifndef SCM_BOOLEAN_H
#define SCM_BOOLEAN_H
/* Copyright 1995-1996,2000,2006,2008-2010,2013,2018
Free Software Foundation, Inc.
This file is part of Guile.
Guile is free software: you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Guile is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public
License along with Guile. If not, see
<https://www.gnu.org/licenses/>. */
#include "libguile/scm.h"
/* Boolean Values. Obviously there are #t and #f, but there is also nil to deal
* with. We choose to treat nil as a false boolean. All options might silently
* break existing code, but this one seems most responsible.
*
*/
/*
* Use these macros if it's important (for correctness)
* that #nil MUST be considered true
*/
#define scm_is_false_and_not_nil(x) (scm_is_eq ((x), SCM_BOOL_F))
#define scm_is_true_or_nil(x) (!scm_is_eq ((x), SCM_BOOL_F))
/*
* Use these macros if #nil will never be tested,
* for increased efficiency.
*/
#define scm_is_false_assume_not_nil(x) (scm_is_eq ((x), SCM_BOOL_F))
#define scm_is_true_assume_not_nil(x) (!scm_is_eq ((x), SCM_BOOL_F))
/*
* See the comments preceeding the definitions of SCM_BOOL_F and
* SCM_MATCHES_BITS_IN_COMMON in scm.h for more information on
* how the following macro works.
*/
#define scm_is_false_or_nil(x) \
(SCM_MATCHES_BITS_IN_COMMON ((x), SCM_ELISP_NIL, SCM_BOOL_F))
#define scm_is_true_and_not_nil(x) (!scm_is_false_or_nil (x))
/* #nil is false. */
#define scm_is_false(x) (scm_is_false_or_nil (x))
#define scm_is_true(x) (!scm_is_false (x))
/*
* Since we know SCM_BOOL_F and SCM_BOOL_T differ by exactly one bit,
* and that SCM_BOOL_F and SCM_ELISP_NIL differ by exactly one bit,
* and that they of course can't be the same bit (or else SCM_BOOL_T
* and SCM_ELISP_NIL be would equal), it follows that SCM_BOOL_T and
* SCM_ELISP_NIL differ by exactly two bits, and these are the bits
* which will be ignored by SCM_MATCHES_BITS_IN_COMMON below.
*
* See the comments preceeding the definitions of SCM_BOOL_F and
* SCM_MATCHES_BITS_IN_COMMON in scm.h for more information.
*
* If SCM_ENABLE_ELISP is true, then scm_is_bool_or_nil(x)
* returns 1 if and only if x is one of the following: SCM_BOOL_F,
* SCM_BOOL_T, SCM_ELISP_NIL, or SCM_XXX_ANOTHER_BOOLEAN_DONT_USE_0.
* Otherwise, it returns 0.
*/
#define scm_is_bool_or_nil(x) \
(SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_T, SCM_ELISP_NIL))
#define scm_is_bool_and_not_nil(x) \
(SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_BOOL_T))
SCM_API int scm_is_bool (SCM);
#define scm_is_bool(x) (scm_is_bool_or_nil (x))
#define scm_from_bool(x) ((x) ? SCM_BOOL_T : SCM_BOOL_F)
SCM_API int scm_to_bool (SCM x);
/* Older spellings for the above routines, kept around for
compatibility. */
#define SCM_FALSEP(x) (scm_is_false (x))
#define SCM_NFALSEP(x) (scm_is_true (x))
#define SCM_BOOLP(x) (scm_is_bool (x))
#define SCM_BOOL(x) (scm_from_bool (x))
#define SCM_NEGATE_BOOL(f) (scm_from_bool (!(f)))
#define SCM_BOOL_NOT(x) (scm_not (x))
/*
* The following macros efficiently implement boolean truth testing as
* expected by most lisps, which treat '() aka SCM_EOL as false.
*
* Since we know SCM_ELISP_NIL and SCM_BOOL_F differ by exactly one
* bit, and that SCM_ELISP_NIL and SCM_EOL differ by exactly one bit,
* and that they of course can't be the same bit (or else SCM_BOOL_F
* and SCM_EOL be would equal), it follows that SCM_BOOL_F and SCM_EOL
* differ by exactly two bits, and these are the bits which will be
* ignored by SCM_MATCHES_BITS_IN_COMMON below.
*
* See the comments preceeding the definitions of SCM_BOOL_F and
* SCM_MATCHES_BITS_IN_COMMON in scm.h for more information.
*
* scm_is_lisp_false(x) returns 1 if and only if x is one of the
* following: SCM_BOOL_F, SCM_ELISP_NIL, SCM_EOL or
* SCM_XXX_ANOTHER_LISP_FALSE_DONT_USE. Otherwise, it returns 0.
*/
#define scm_is_lisp_false(x) \
(SCM_MATCHES_BITS_IN_COMMON ((x), SCM_BOOL_F, SCM_EOL))
SCM_API SCM scm_not (SCM x);
SCM_API SCM scm_boolean_p (SCM obj);
SCM_API SCM scm_nil_p (SCM obj);
#define SCM_VALIDATE_BOOL(pos, flag) \
do { \
SCM_ASSERT_TYPE (scm_is_bool (flag), flag, pos, FUNC_NAME, "boolean"); \
} while (0)
#define SCM_VALIDATE_BOOL_COPY(pos, flag, cvar) \
do { \
SCM_ASSERT (scm_is_bool (flag), flag, pos, FUNC_NAME); \
cvar = scm_to_bool (flag); \
} while (0)
SCM_INTERNAL void scm_init_boolean (void);
#endif /* SCM_BOOLEAN_H */
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