581 lines
9.9 KiB
C
581 lines
9.9 KiB
C
/* $NetBSD: expr.c,v 1.7 1995/09/28 05:37:31 tls Exp $ */
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/*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Ozan Yigit at York University.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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#if 0
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static char sccsid[] = "@(#)expr.c 8.2 (Berkeley) 4/29/95";
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#else
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static char rcsid[] = "$NetBSD: expr.c,v 1.7 1995/09/28 05:37:31 tls Exp $";
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#endif
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#endif /* not lint */
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#include <sys/cdefs.h>
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#include <stdio.h>
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/*
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* expression evaluator: performs a standard recursive
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* descent parse to evaluate any expression permissible
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* within the following grammar:
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*
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* expr : query EOS
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* query : lor
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* | lor "?" query ":" query
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* lor : land { "||" land }
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* land : not { "&&" not }
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* not : eqrel
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* | '!' not
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* eqrel : shift { eqrelop shift }
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* shift : primary { shop primary }
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* primary : term { addop term }
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* term : exp { mulop exp }
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* exp : unary { expop unary }
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* unary : factor
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* | unop unary
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* factor : constant
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* | "(" query ")"
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* constant: num
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* | "'" CHAR "'"
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* num : DIGIT
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* | DIGIT num
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* shop : "<<"
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* | ">>"
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* eqrel : "="
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* | "=="
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* | "!="
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* | "<"
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* | ">"
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* | "<="
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* | ">="
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*
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*
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* This expression evaluator is lifted from a public-domain
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* C Pre-Processor included with the DECUS C Compiler distribution.
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* It is hacked somewhat to be suitable for m4.
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*
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* Originally by: Mike Lutz
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* Bob Harper
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*/
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#define TRUE 1
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#define FALSE 0
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#define EOS (char) 0
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#define EQL 0
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#define NEQ 1
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#define LSS 2
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#define LEQ 3
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#define GTR 4
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#define GEQ 5
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#define OCTAL 8
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#define DECIMAL 10
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static char *nxtch; /* Parser scan pointer */
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static int query __P((void));
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static int lor __P((void));
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static int land __P((void));
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static int not __P((void));
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static int eqrel __P((void));
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static int shift __P((void));
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static int primary __P((void));
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static int term __P((void));
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static int exp __P((void));
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static int unary __P((void));
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static int factor __P((void));
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static int constant __P((void));
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static int num __P((void));
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static int geteqrel __P((void));
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static int skipws __P((void));
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static void experr __P((char *));
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/*
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* For longjmp
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*/
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#include <setjmp.h>
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static jmp_buf expjump;
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/*
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* macros:
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* ungetch - Put back the last character examined.
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* getch - return the next character from expr string.
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*/
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#define ungetch() nxtch--
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#define getch() *nxtch++
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int
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expr(expbuf)
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char *expbuf;
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{
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register int rval;
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nxtch = expbuf;
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if (setjmp(expjump) != 0)
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return FALSE;
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rval = query();
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if (skipws() == EOS)
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return rval;
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printf("m4: ill-formed expression.\n");
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return FALSE;
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}
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/*
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* query : lor | lor '?' query ':' query
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*/
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static int
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query()
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{
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register int bool, true_val, false_val;
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bool = lor();
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if (skipws() != '?') {
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ungetch();
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return bool;
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}
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true_val = query();
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if (skipws() != ':')
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experr("bad query");
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false_val = query();
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return bool ? true_val : false_val;
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}
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/*
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* lor : land { '||' land }
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*/
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static int
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lor()
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{
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register int c, vl, vr;
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vl = land();
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while ((c = skipws()) == '|') {
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if (getch() != '|')
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ungetch();
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vr = land();
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vl = vl || vr;
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}
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ungetch();
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return vl;
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}
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/*
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* land : not { '&&' not }
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*/
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static int
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land()
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{
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register int c, vl, vr;
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vl = not();
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while ((c = skipws()) == '&') {
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if (getch() != '&')
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ungetch();
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vr = not();
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vl = vl && vr;
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}
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ungetch();
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return vl;
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}
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/*
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* not : eqrel | '!' not
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*/
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static int
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not()
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{
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register int val, c;
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if ((c = skipws()) == '!' && getch() != '=') {
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ungetch();
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val = not();
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return !val;
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}
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if (c == '!')
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ungetch();
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ungetch();
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return eqrel();
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}
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/*
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* eqrel : shift { eqrelop shift }
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*/
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static int
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eqrel()
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{
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register int vl, vr, eqrel;
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vl = shift();
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while ((eqrel = geteqrel()) != -1) {
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vr = shift();
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switch (eqrel) {
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case EQL:
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vl = (vl == vr);
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break;
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case NEQ:
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vl = (vl != vr);
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break;
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case LEQ:
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vl = (vl <= vr);
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break;
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case LSS:
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vl = (vl < vr);
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break;
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case GTR:
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vl = (vl > vr);
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break;
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case GEQ:
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vl = (vl >= vr);
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break;
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}
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}
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return vl;
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}
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/*
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* shift : primary { shop primary }
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*/
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static int
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shift()
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{
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register int vl, vr, c;
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vl = primary();
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while (((c = skipws()) == '<' || c == '>') && getch() == c) {
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vr = primary();
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if (c == '<')
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vl <<= vr;
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else
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vl >>= vr;
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}
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if (c == '<' || c == '>')
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ungetch();
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ungetch();
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return vl;
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}
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/*
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* primary : term { addop term }
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*/
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static int
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primary()
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{
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register int c, vl, vr;
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vl = term();
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while ((c = skipws()) == '+' || c == '-') {
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vr = term();
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if (c == '+')
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vl += vr;
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else
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vl -= vr;
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}
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ungetch();
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return vl;
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}
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/*
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* <term> := <exp> { <mulop> <exp> }
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*/
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static int
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term()
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{
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register int c, vl, vr;
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vl = exp();
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while ((c = skipws()) == '*' || c == '/' || c == '%') {
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vr = exp();
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switch (c) {
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case '*':
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vl *= vr;
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break;
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case '/':
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vl /= vr;
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break;
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case '%':
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vl %= vr;
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break;
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}
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}
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ungetch();
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return vl;
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}
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/*
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* <term> := <unary> { <expop> <unary> }
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*/
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static int
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exp()
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{
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register c, vl, vr, n;
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vl = unary();
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switch (c = skipws()) {
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case '*':
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if (getch() != '*') {
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ungetch();
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break;
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}
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case '^':
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vr = exp();
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n = 1;
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while (vr-- > 0)
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n *= vl;
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return n;
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}
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ungetch();
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return vl;
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}
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/*
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* unary : factor | unop unary
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*/
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static int
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unary()
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{
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register int val, c;
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if ((c = skipws()) == '+' || c == '-' || c == '~') {
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val = unary();
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switch (c) {
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case '+':
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return val;
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case '-':
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return -val;
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case '~':
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return ~val;
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}
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}
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ungetch();
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return factor();
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}
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/*
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* factor : constant | '(' query ')'
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*/
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static int
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factor()
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{
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register int val;
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if (skipws() == '(') {
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val = query();
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if (skipws() != ')')
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experr("bad factor");
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return val;
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}
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ungetch();
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return constant();
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}
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/*
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* constant: num | 'char'
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* Note: constant() handles multi-byte constants
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*/
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static int
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constant()
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{
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register int i;
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register int value;
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register char c;
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int v[sizeof(int)];
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if (skipws() != '\'') {
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ungetch();
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return num();
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}
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for (i = 0; i < sizeof(int); i++) {
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if ((c = getch()) == '\'') {
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ungetch();
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break;
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}
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if (c == '\\') {
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switch (c = getch()) {
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case '0':
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case '1':
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case '2':
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case '3':
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case '4':
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case '5':
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case '6':
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case '7':
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ungetch();
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c = num();
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break;
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case 'n':
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c = 012;
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break;
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case 'r':
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c = 015;
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break;
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case 't':
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c = 011;
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break;
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case 'b':
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c = 010;
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break;
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case 'f':
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c = 014;
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break;
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}
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}
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v[i] = c;
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}
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if (i == 0 || getch() != '\'')
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experr("illegal character constant");
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for (value = 0; --i >= 0;) {
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value <<= 8;
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value += v[i];
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}
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return value;
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}
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/*
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* num : digit | num digit
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*/
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static int
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num()
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{
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register int rval, c, base;
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int ndig;
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base = ((c = skipws()) == '0') ? OCTAL : DECIMAL;
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rval = 0;
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ndig = 0;
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while (c >= '0' && c <= (base == OCTAL ? '7' : '9')) {
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rval *= base;
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rval += (c - '0');
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c = getch();
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ndig++;
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}
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ungetch();
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if (ndig == 0)
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experr("bad constant");
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return rval;
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}
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/*
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* eqrel : '=' | '==' | '!=' | '<' | '>' | '<=' | '>='
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*/
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static int
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geteqrel()
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{
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register int c1, c2;
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c1 = skipws();
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c2 = getch();
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switch (c1) {
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case '=':
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if (c2 != '=')
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ungetch();
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return EQL;
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case '!':
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if (c2 == '=')
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return NEQ;
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ungetch();
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ungetch();
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return -1;
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case '<':
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if (c2 == '=')
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return LEQ;
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ungetch();
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return LSS;
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case '>':
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if (c2 == '=')
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return GEQ;
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ungetch();
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return GTR;
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default:
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ungetch();
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ungetch();
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return -1;
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}
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}
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/*
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* Skip over any white space and return terminating char.
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*/
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static int
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skipws()
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{
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register char c;
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while ((c = getch()) <= ' ' && c > EOS)
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;
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return c;
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}
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/*
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* resets environment to eval(), prints an error
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* and forces eval to return FALSE.
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*/
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static void
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experr(msg)
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char *msg;
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{
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printf("m4: %s in expr.\n", msg);
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longjmp(expjump, -1);
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}
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