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0c0a658c56
* libguile/boolean.c (scm_nil_p): Improve docstring. * doc/ref/api-languages.texi (Nil): Add documentation for 'nil?', along with a description of how Elisp interprets Scheme booleans and end-of-list.
120 lines
3.3 KiB
C
120 lines
3.3 KiB
C
/* Copyright 1995-1996,2000-2001,2006,2008-2011,2018,2019
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Free Software Foundation, Inc.
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This file is part of Guile.
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Guile is free software: you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published
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by the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Guile is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with Guile. If not, see
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<https://www.gnu.org/licenses/>. */
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include "error.h"
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#include "gsubr.h"
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#include "verify.h"
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#include "boolean.h"
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/*
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* These compile-time tests verify the properties needed for the
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* efficient test macros defined in boolean.h, which are defined in
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* terms of the SCM_MATCHES_BITS_IN_COMMON macro.
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*
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* See the comments preceeding the definitions of SCM_BOOL_F and
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* SCM_MATCHES_BITS_IN_COMMON in scm.h for more information.
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*/
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verify (SCM_BITS_DIFFER_IN_EXACTLY_ONE_BIT_POSITION \
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(SCM_BOOL_F_BITS, SCM_BOOL_T_BITS));
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verify (SCM_BITS_DIFFER_IN_EXACTLY_ONE_BIT_POSITION \
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(SCM_ELISP_NIL_BITS, SCM_BOOL_F_BITS));
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verify (SCM_BITS_DIFFER_IN_EXACTLY_ONE_BIT_POSITION \
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(SCM_ELISP_NIL_BITS, SCM_EOL_BITS));
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verify (SCM_BITS_DIFFER_IN_EXACTLY_TWO_BIT_POSITIONS \
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(SCM_ELISP_NIL_BITS, SCM_BOOL_F_BITS, SCM_BOOL_T_BITS, \
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SCM_XXX_ANOTHER_BOOLEAN_DONT_USE_0));
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verify (SCM_BITS_DIFFER_IN_EXACTLY_TWO_BIT_POSITIONS \
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(SCM_ELISP_NIL_BITS, SCM_BOOL_F_BITS, SCM_EOL_BITS, \
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SCM_XXX_ANOTHER_LISP_FALSE_DONT_USE));
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SCM_DEFINE (scm_not, "not", 1, 0, 0,
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(SCM x),
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"Return @code{#t} iff @var{x} is false, else return @code{#f}.")
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#define FUNC_NAME s_scm_not
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{
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return scm_from_bool (scm_is_false (x));
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_nil_p, "nil?", 1, 0, 0,
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(SCM x),
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"Return @code{#t} if @var{x} would be interpreted as @code{nil}\n"
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"by Emacs Lisp code, else return @code{#f}.\n"
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"\n"
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"@example\n"
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"(nil? #nil) @result{} #t\n"
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"(nil? #f) @result{} #t\n"
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"(nil? '()) @result{} #t\n"
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"(nil? 3) @result{} #f\n"
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"@end example")
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#define FUNC_NAME s_scm_nil_p
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{
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return scm_from_bool (scm_is_lisp_false (x));
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}
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#undef FUNC_NAME
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SCM_DEFINE (scm_boolean_p, "boolean?", 1, 0, 0,
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(SCM obj),
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"Return @code{#t} iff @var{obj} is @code{#t} or false.")
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#define FUNC_NAME s_scm_boolean_p
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{
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return scm_from_bool (scm_is_bool (obj));
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}
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#undef FUNC_NAME
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int
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scm_to_bool (SCM x)
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{
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if (scm_is_false (x))
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return 0;
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else if (scm_is_eq (x, SCM_BOOL_T))
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return 1;
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else
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scm_wrong_type_arg (NULL, 0, x);
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}
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/* We keep this primitive as a function in addition to the same-named macro
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because some applications (e.g., GNU LilyPond 2.13.9) expect it to be a
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function. */
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#undef scm_is_bool
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int
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scm_is_bool (SCM obj)
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{
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/* This must match the macro definition of `scm_is_bool ()'. */
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return scm_is_bool_or_nil (obj);
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}
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void
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scm_init_boolean ()
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{
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#include "boolean.x"
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}
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