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/*===========================================================================
* Filename : module-srfi2.c
* About : SRFI-2 AND-LET*: an AND with local bindings, a guarded LET*
* special form
*
* Copyright (C) 2005 Kazuki Ohta <mover AT hct.zaq.ne.jp>
* Copyright (C) 2005-2006 Jun Inoue <jun.lambda AT gmail.com>
* Copyright (C) 2005-2006 YAMAMOTO Kengo <yamaken AT bp.iij4u.or.jp>
* Copyright (c) 2007-2008 SigScheme Project <uim-en AT googlegroups.com>
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of authors nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
* IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
===========================================================================*/
#include <config.h>
#include "sigscheme.h"
#include "sigschemeinternal.h"
/*=======================================
File Local Macro Definitions
=======================================*/
/*=======================================
File Local Type Definitions
=======================================*/
/*=======================================
Variable Definitions
=======================================*/
#include "functable-srfi2.c"
/*=======================================
File Local Function Declarations
=======================================*/
/*=======================================
Function Definitions
=======================================*/
SCM_EXPORT void
scm_initialize_srfi2(void)
{
scm_register_funcs(scm_functable_srfi2);
}
SCM_EXPORT ScmObj
scm_s_srfi2_and_letstar(ScmObj claws, ScmObj body, ScmEvalState *eval_state)
{
ScmObj env, claw, var, val, exp;
DECLARE_FUNCTION("and-let*", syntax_variadic_tailrec_1);
env = eval_state->env;
/*=======================================================================
(and-let* <claws> <body>)
<claws> ::= '() | (cons <claw> <claws>)
<claw> ::= (<variable> <expression>) | (<expression>)
| <bound-variable>
=======================================================================*/
val = SCM_TRUE;
FOR_EACH (claw, claws) {
if (CONSP(claw)) {
if (NULLP(CDR(claw))) {
/* (<expression>) */
exp = CAR(claw);
val = EVAL(exp, env);
CHECK_VALID_EVALED_VALUE(val);
} else if (IDENTIFIERP(CAR(claw))) {
/* (<variable> <expression>) */
if (!LIST_2_P(claw))
goto err;
var = CAR(claw);
exp = CADR(claw);
val = EVAL(exp, env);
CHECK_VALID_EVALED_VALUE(val);
env = scm_extend_environment(LIST_1(var), LIST_1(val), env);
} else {
goto err;
}
} else if (IDENTIFIERP(claw)) {
/* <bound-variable> */
val = EVAL(claw, env);
CHECK_VALID_EVALED_VALUE(val);
} else {
goto err;
}
if (FALSEP(val)) {
eval_state->ret_type = SCM_VALTYPE_AS_IS;
return SCM_FALSE;
}
}
if (!NULLP(claws))
goto err;
eval_state->env = env;
/* SRFI-2 Formal (Denotational) Semantics:
* eval[ (AND-LET* (CLAW) ), env] = eval_claw[ CLAW, env ]
* eval[ (AND-LET* () ), env] = #t */
if (NULLP(body)) {
eval_state->ret_type = SCM_VALTYPE_AS_IS;
return val;
} else {
return scm_s_body(body, eval_state);
}
err:
ERR_OBJ("invalid claws form", claws);
/* NOTREACHED */
return SCM_FALSE;
}
|
