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/* Simple parser and scanner in Java. -*- Java -*-
Copyright (C) 2018-2021 Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
%language "Java"
%define api.parser.class {Calc}
%define api.parser.public
%define parse.error verbose
%code imports {
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StreamTokenizer;
}
%code {
public static void main(String[] args) throws IOException {
CalcLexer l = new CalcLexer(System.in);
Calc p = new Calc(l);
if (!p.parse())
System.exit(1);
}
}
/* Bison Declarations */
%token <Integer> NUM "number"
%type <Integer> exp
%nonassoc '=' /* comparison */
%left '-' '+'
%left '*' '/'
%precedence NEG /* negation--unary minus */
%right '^' /* exponentiation */
/* Grammar follows */
%%
input:
line
| input line
;
line:
'\n'
| exp '\n' { System.out.println($exp); }
| error '\n'
;
exp:
NUM { $$ = $1; }
| exp '=' exp
{
if ($1.intValue() != $3.intValue())
yyerror("calc: error: " + $1 + " != " + $3);
}
| exp '+' exp { $$ = $1 + $3; }
| exp '-' exp { $$ = $1 - $3; }
| exp '*' exp { $$ = $1 * $3; }
| exp '/' exp { $$ = $1 / $3; }
| '-' exp %prec NEG { $$ = -$2; }
| exp '^' exp { $$ = (int) Math.pow($1, $3); }
| '(' exp ')' { $$ = $2; }
| '(' error ')' { $$ = 1111; }
| '!' { $$ = 0; return YYERROR; }
| '-' error { $$ = 0; return YYERROR; }
;
%%
class CalcLexer implements Calc.Lexer {
StreamTokenizer st;
public CalcLexer(InputStream is) {
st = new StreamTokenizer(new InputStreamReader(is));
st.resetSyntax();
st.eolIsSignificant(true);
st.whitespaceChars('\t', '\t');
st.whitespaceChars(' ', ' ');
st.wordChars('0', '9');
}
public void yyerror(String s) {
System.err.println(s);
}
Integer yylval;
public Object getLVal() {
return yylval;
}
public int yylex() throws IOException {
int ttype = st.nextToken();
switch (ttype) {
case StreamTokenizer.TT_EOF:
return YYEOF;
case StreamTokenizer.TT_EOL:
return (int) '\n';
case StreamTokenizer.TT_WORD:
yylval = Integer.parseInt(st.sval);
return NUM;
default:
return ttype;
}
}
}
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