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/* Copyright 1995-2011,2018
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/>. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <alloca.h>
#include "alist.h"
#include "async.h"
#include "continuations.h"
#include "debug.h"
#include "deprecation.h"
#include "dynwind.h"
#include "eq.h"
#include "eval.h"
#include "feature.h"
#include "fluids.h"
#include "goops.h"
#include "gsubr.h"
#include "hash.h"
#include "hashtab.h"
#include "list.h"
#include "macros.h"
#include "memoize.h"
#include "modules.h"
#include "ports.h"
#include "print.h"
#include "procprop.h"
#include "procs.h"
#include "programs.h"
#include "smob.h"
#include "srcprop.h"
#include "stackchk.h"
#include "strings.h"
#include "threads.h"
#include "throw.h"
#include "values.h"
#include "promises.h"
scm_t_bits scm_tc16_promise;
SCM_DEFINE (scm_make_promise, "make-promise", 1, 0, 0,
(SCM thunk),
"Create a new promise object.\n\n"
"@code{make-promise} is a procedural form of @code{delay}.\n"
"These two expressions are equivalent:\n"
"@lisp\n"
"(delay @var{exp})\n"
"(make-promise (lambda () @var{exp}))\n"
"@end lisp\n")
#define FUNC_NAME s_scm_make_promise
{
SCM_VALIDATE_THUNK (1, thunk);
SCM_RETURN_NEWSMOB2 (scm_tc16_promise,
SCM_UNPACK (thunk),
SCM_UNPACK (scm_make_recursive_mutex ()));
}
#undef FUNC_NAME
static int
promise_print (SCM exp, SCM port, scm_print_state *pstate)
{
int writingp = SCM_WRITINGP (pstate);
scm_puts ("#<promise ", port);
SCM_SET_WRITINGP (pstate, 1);
scm_iprin1 (SCM_PROMISE_DATA (exp), port, pstate);
SCM_SET_WRITINGP (pstate, writingp);
scm_putc ('>', port);
return !0;
}
SCM_DEFINE (scm_force, "force", 1, 0, 0,
(SCM promise),
"If @var{promise} has not been computed yet, compute and\n"
"return @var{promise}, otherwise just return the previously computed\n"
"value.")
#define FUNC_NAME s_scm_force
{
SCM_VALIDATE_SMOB (1, promise, promise);
scm_lock_mutex (SCM_PROMISE_MUTEX (promise));
if (!SCM_PROMISE_COMPUTED_P (promise))
{
SCM ans = scm_call_0 (SCM_PROMISE_DATA (promise));
if (!SCM_PROMISE_COMPUTED_P (promise))
{
SCM_SET_PROMISE_DATA (promise, ans);
SCM_SET_PROMISE_COMPUTED (promise);
}
}
scm_unlock_mutex (SCM_PROMISE_MUTEX (promise));
return SCM_PROMISE_DATA (promise);
}
#undef FUNC_NAME
SCM_DEFINE (scm_promise_p, "promise?", 1, 0, 0,
(SCM obj),
"Return true if @var{obj} is a promise, i.e. a delayed computation\n"
"(@pxref{Delayed evaluation,,,r5rs.info,The Revised^5 Report on Scheme}).")
#define FUNC_NAME s_scm_promise_p
{
return scm_from_bool (SCM_TYP16_PREDICATE (scm_tc16_promise, obj));
}
#undef FUNC_NAME
void
scm_init_promises ()
{
scm_tc16_promise = scm_make_smob_type ("promise", 0);
scm_set_smob_print (scm_tc16_promise, promise_print);
#include "promises.x"
scm_add_feature ("delay");
}
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