601 lines
13 KiB
C
601 lines
13 KiB
C
/*
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* Copyright (c) 1989 The Regents of the University of California.
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* 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.
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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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static char sccsid[] = "@(#)expr.c 5.3 (Berkeley) 2/26/91";
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#endif /* not lint */
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#include <setjmp.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 : bor { "&&" bor }
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* bor : bxor { "|" bxor }
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* bxor : band { "^" band }
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* band : eql { "&" eql }
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* eql : relat { eqrel relat }
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* relat : shift { rel shift }
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* shift : primary { shop primary }
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* primary : term { addop term }
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* term : unary { mulop 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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* eqlrel : "="
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* | "=="
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* | "!="
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* rel : "<"
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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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/*
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* For longjmp
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*/
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static jmp_buf expjump;
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/*
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* macros:
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*
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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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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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experr("Ill-formed expression");
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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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*/
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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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*/
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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()) == '|' && getch() == '|') {
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vr = land();
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vl = vl || vr;
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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(vl);
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}
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/*
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* land : bor { '&&' bor }
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*
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*/
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land()
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{
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register int c, vl, vr;
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vl = bor();
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while ((c = skipws()) == '&' && getch() == '&') {
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vr = bor();
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vl = vl && vr;
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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(vl);
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}
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/*
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* bor : bxor { '|' bxor }
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*
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*/
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bor()
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{
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register int vl, vr, c;
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vl = bxor();
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while ((c = skipws()) == '|' && getch() != '|') {
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ungetch();
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vr = bxor();
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vl |= vr;
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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(vl);
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}
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/*
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* bxor : band { '^' band }
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*
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*/
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bxor()
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{
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register int vl, vr;
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vl = band();
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while (skipws() == '^') {
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vr = band();
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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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* band : eql { '&' eql }
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*
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*/
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band()
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{
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register int vl, vr, c;
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vl = eql();
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while ((c = skipws()) == '&' && getch() != '&') {
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ungetch();
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vr = eql();
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vl &= vr;
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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(vl);
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}
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/*
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* eql : relat { eqrel relat }
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*
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*/
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eql()
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{
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register int vl, vr, rel;
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vl = relat();
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while ((rel = geteql()) != -1) {
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vr = relat();
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switch (rel) {
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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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}
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}
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return(vl);
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}
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/*
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* relat : shift { rel shift }
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*
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*/
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relat()
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{
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register int vl, vr, rel;
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vl = shift();
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while ((rel = getrel()) != -1) {
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vr = shift();
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switch (rel) {
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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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*/
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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 == '>') && c == getch()) {
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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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*/
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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> := <unary> { <mulop> <unary> }
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*
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*/
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term()
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{
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register int c, vl, vr;
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vl = unary();
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while ((c = skipws()) == '*' || c == '/' || c == '%') {
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vr = unary();
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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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* unary : factor | unop unary
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*
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*/
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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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*/
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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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*
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*/
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constant()
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{
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/*
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* Note: constant() handles multi-byte constants
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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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*/
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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)
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return(rval);
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experr("Bad constant");
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}
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/*
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* eqlrel : '=' | '==' | '!='
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*
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*/
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geteql()
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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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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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* rel : '<' | '>' | '<=' | '>='
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*
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*/
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getrel()
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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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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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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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* Error handler - resets environment to eval(), prints an error,
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* and returns FALSE.
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*/
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experr(msg)
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char *msg;
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{
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printf("mp: %s\n",msg);
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longjmp(expjump, -1); /* Force eval() to return FALSE */
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}
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