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+%{
+/*	$NetBSD: arith.y,v 1.15 2002/11/24 22:35:39 christos Exp $	*/
+
+/*-
+ * Copyright (c) 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Kenneth Almquist.
+ *
+ * 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. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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 <sys/cdefs.h>
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)arith.y	8.3 (Berkeley) 5/4/95";
+#else
+__RCSID("$NetBSD: arith.y,v 1.15 2002/11/24 22:35:39 christos Exp $");
+#endif
+#endif /* not lint */
+
+#include <stdlib.h>
+#include "expand.h"
+#include "shell.h"
+#include "error.h"
+#include "output.h"
+#include "memalloc.h"
+
+const char *arith_buf, *arith_startbuf;
+
+#ifndef YYBISON
+int yyparse(void);
+#endif
+void yyerror(const char *);
+#ifdef TESTARITH
+int main(int , char *[]);
+int error(char *);
+#endif
+
+%}
+%token ARITH_NUM ARITH_LPAREN ARITH_RPAREN
+
+%left ARITH_OR
+%left ARITH_AND
+%left ARITH_BOR
+%left ARITH_BXOR
+%left ARITH_BAND
+%left ARITH_EQ ARITH_NE
+%left ARITH_LT ARITH_GT ARITH_GE ARITH_LE
+%left ARITH_LSHIFT ARITH_RSHIFT
+%left ARITH_ADD ARITH_SUB
+%left ARITH_MUL ARITH_DIV ARITH_REM
+%left ARITH_UNARYMINUS ARITH_UNARYPLUS ARITH_NOT ARITH_BNOT
+%%
+
+exp:	expr {
+			return ($1);
+	}
+	;
+
+
+expr:	ARITH_LPAREN expr ARITH_RPAREN { $$ = $2; }
+	| expr ARITH_OR expr	{ $$ = $1 || $3; }
+	| expr ARITH_AND expr	{ $$ = $1 && $3; }
+	| expr ARITH_BOR expr	{ $$ = $1 | $3; }
+	| expr ARITH_BXOR expr	{ $$ = $1 ^ $3; }
+	| expr ARITH_BAND expr	{ $$ = $1 & $3; }
+	| expr ARITH_EQ expr	{ $$ = $1 == $3; }
+	| expr ARITH_GT expr	{ $$ = $1 > $3; }
+	| expr ARITH_GE expr	{ $$ = $1 >= $3; }
+	| expr ARITH_LT expr	{ $$ = $1 < $3; }
+	| expr ARITH_LE expr	{ $$ = $1 <= $3; }
+	| expr ARITH_NE expr	{ $$ = $1 != $3; }
+	| expr ARITH_LSHIFT expr { $$ = $1 << $3; }
+	| expr ARITH_RSHIFT expr { $$ = $1 >> $3; }
+	| expr ARITH_ADD expr	{ $$ = $1 + $3; }
+	| expr ARITH_SUB expr	{ $$ = $1 - $3; }
+	| expr ARITH_MUL expr	{ $$ = $1 * $3; }
+	| expr ARITH_DIV expr	{
+			if ($3 == 0)
+				yyerror("division by zero");
+			$$ = $1 / $3;
+		}
+	| expr ARITH_REM expr   {
+			if ($3 == 0)
+				yyerror("division by zero");
+			$$ = $1 % $3;
+		}
+	| ARITH_NOT expr	{ $$ = !($2); }
+	| ARITH_BNOT expr	{ $$ = ~($2); }
+	| ARITH_SUB expr %prec ARITH_UNARYMINUS { $$ = -($2); }
+	| ARITH_ADD expr %prec ARITH_UNARYPLUS { $$ = $2; }
+	| ARITH_NUM
+	;
+%%
+int
+arith(s)
+	const char *s;
+{
+	long result;
+
+	arith_buf = arith_startbuf = s;
+
+	INTOFF;
+	result = yyparse();
+	arith_lex_reset();	/* reprime lex */
+	INTON;
+
+	return (result);
+}
+
+
+/*
+ *  The exp(1) builtin.
+ */
+int
+expcmd(argc, argv)
+	int argc;
+	char **argv;
+{
+	const char *p;
+	char *concat;
+	char **ap;
+	long i;
+
+	if (argc > 1) {
+		p = argv[1];
+		if (argc > 2) {
+			/*
+			 * concatenate arguments
+			 */
+			STARTSTACKSTR(concat);
+			ap = argv + 2;
+			for (;;) {
+				while (*p)
+					STPUTC(*p++, concat);
+				if ((p = *ap++) == NULL)
+					break;
+				STPUTC(' ', concat);
+			}
+			STPUTC('\0', concat);
+			p = grabstackstr(concat);
+		}
+	} else
+		p = nullstr;
+
+	i = arith(p);
+
+	out1fmt("%ld\n", i);
+	return (! i);
+}
+
+/*************************/
+#ifdef TEST_ARITH
+#include <stdio.h>
+main(argc, argv)
+	char *argv[];
+{
+	printf("%d\n", exp(argv[1]));
+}
+error(s)
+	char *s;
+{
+	fprintf(stderr, "exp: %s\n", s);
+	exit(1);
+}
+#endif
+
+void
+yyerror(s)
+	const char *s;
+{
+
+#ifndef YYBISON
+	yyerrok;
+#endif
+	yyclearin;
+	arith_lex_reset();	/* reprime lex */
+	error("arithmetic expression: %s: \"%s\"", s, arith_startbuf);
+	/* NOTREACHED */
+}