318 lines
7.3 KiB
Plaintext
318 lines
7.3 KiB
Plaintext
/* Parser and scanner for calc in Java. -*- Java -*-
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Copyright (C) 2018-2021 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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%language "Java"
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%define api.parser.class {Calc}
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%define api.parser.public
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%define api.push-pull push
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// Customized syntax error messages (see reportSyntaxError)...
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%define parse.error custom
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// ... with locations...
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%locations
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// ... and accurate list of expected tokens.
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%define parse.lac full
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%define parse.trace
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%code imports {
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.InputStreamReader;
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import java.io.Reader;
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import java.io.StreamTokenizer;
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import java.nio.CharBuffer;
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}
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%code {
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public static void main(String[] args) throws IOException {
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CalcLexer scanner = new CalcLexer(System.in);
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Calc parser = new Calc(scanner);
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for (String arg : args)
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if (arg.equals("-p"))
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parser.setDebugLevel(1);
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int status;
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do {
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int token = scanner.getToken();
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Object lval = scanner.getValue();
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Calc.Location yyloc = scanner.getLocation();
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status = parser.push_parse(token, lval, yyloc);
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} while (status == Calc.YYPUSH_MORE);
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if (status != Calc.YYACCEPT)
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System.exit(1);
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}
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static String i18n(String s) {
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return s;
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}
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}
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/* Bison Declarations */
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%token
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BANG "!"
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PLUS "+"
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MINUS "-"
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STAR "*"
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SLASH "/"
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CARET "^"
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LPAREN "("
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RPAREN ")"
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EQUAL "="
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EOL _("end of line")
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<Integer>
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NUM _("number")
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%type <Integer> exp
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%nonassoc "=" /* comparison */
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%left "-" "+"
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%left "*" "/"
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%precedence NEG /* negation--unary minus */
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%right "^" /* exponentiation */
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/* Grammar follows */
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%%
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input:
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line
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| input line
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;
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line:
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EOL
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| exp EOL { System.out.println($exp); }
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| error EOL
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;
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exp:
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NUM { $$ = $1; }
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| exp "=" exp
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{
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if ($1.intValue() != $3.intValue())
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yyerror(@$, "calc: error: " + $1 + " != " + $3);
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}
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| exp "+" exp { $$ = $1 + $3; }
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| exp "-" exp { $$ = $1 - $3; }
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| exp "*" exp { $$ = $1 * $3; }
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| exp "/" exp { $$ = $1 / $3; }
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| "-" exp %prec NEG { $$ = -$2; }
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| exp "^" exp { $$ = (int) Math.pow($1, $3); }
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| "(" exp ")" { $$ = $2; }
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| "(" error ")" { $$ = 1111; }
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| "!" { $$ = 0; return YYERROR; }
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| "-" error { $$ = 0; return YYERROR; }
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;
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%%
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class CalcLexer implements Calc.Lexer {
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StreamTokenizer st;
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PositionReader reader;
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public CalcLexer(InputStream is) {
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reader = new PositionReader(new InputStreamReader(is));
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st = new StreamTokenizer(reader);
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st.resetSyntax();
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st.eolIsSignificant(true);
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st.wordChars('0', '9');
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}
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Position start = new Position(1, 0);
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Position end = new Position(1, 0);
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/**
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* The location of the last token read.
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* Implemented with getStartPos and getEndPos in pull parsers.
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*/
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public Calc.Location getLocation() {
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return new Calc.Location(new Position(start), new Position(end));
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}
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/**
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* Build and emit a syntax error message.
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*/
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public void reportSyntaxError(Calc.Context ctx) {
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System.err.print(ctx.getLocation() + ": syntax error");
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{
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final int TOKENMAX = 10;
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Calc.SymbolKind[] arg = new Calc.SymbolKind[TOKENMAX];
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int n = ctx.getExpectedTokens(arg, TOKENMAX);
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for (int i = 0; i < n; ++i)
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System.err.print((i == 0 ? ": expected " : " or ")
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+ arg[i].getName());
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}
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{
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Calc.SymbolKind lookahead = ctx.getToken();
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if (lookahead != null)
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System.err.print(" before " + lookahead.getName());
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}
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System.err.println("");
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}
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/**
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* Emit an error referring to the given location in a user-defined way.
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*
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* @@param loc The location of the element to which the
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* error message is related.
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* @@param msg The string for the error message.
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*/
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public void yyerror(Calc.Location loc, String msg) {
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if (loc == null)
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System.err.println(msg);
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else
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System.err.println(loc + ": " + msg);
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}
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Integer yylval;
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/**
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* The value of the last token read. Called getLVal in pull parsers.
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*/
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public Object getValue() {
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return yylval;
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}
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/**
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* Fetch the next token. Called yylex in pull parsers.
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*/
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public int getToken() throws IOException {
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start.set(reader.getPosition());
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int ttype = st.nextToken();
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end.set(reader.getPosition());
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switch (ttype) {
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case StreamTokenizer.TT_EOF:
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return YYEOF;
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case StreamTokenizer.TT_EOL:
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end.line += 1;
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end.column = 0;
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return EOL;
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case StreamTokenizer.TT_WORD:
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yylval = Integer.parseInt(st.sval);
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end.set(reader.getPreviousPosition());
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return NUM;
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case ' ': case '\t':
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return getToken();
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case '!':
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return BANG;
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case '+':
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return PLUS;
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case '-':
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return MINUS;
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case '*':
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return STAR;
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case '/':
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return SLASH;
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case '^':
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return CARET;
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case '(':
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return LPAREN;
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case ')':
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return RPAREN;
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case '=':
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return EQUAL;
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default:
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throw new AssertionError("invalid character: " + ttype);
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}
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}
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}
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/**
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* A class defining a point in the input.
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*/
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class Position {
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public int line = 1;
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public int column = 1;
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public Position() {
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line = 1;
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column = 1;
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}
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public Position(int l, int t) {
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line = l;
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column = t;
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}
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public Position(Position p) {
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line = p.line;
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column = p.column;
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}
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public void set(Position p) {
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line = p.line;
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column = p.column;
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}
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public boolean equals(Position l) {
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return l.line == line && l.column == column;
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}
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public String toString() {
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return Integer.toString(line) + "." + Integer.toString(column);
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}
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public int line() {
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return line;
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}
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public int column() {
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return column;
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}
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}
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/**
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* A Stream reader that keeps track of the current Position.
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*/
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class PositionReader extends BufferedReader {
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private Position position = new Position();
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// Position before the latest call to "read", i.e. position
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// of the last character of the current token.
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private Position previousPosition = new Position();
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public PositionReader(Reader reader) {
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super(reader);
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}
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public int read() throws IOException {
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previousPosition.set(position);
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int res = super.read();
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if (res > -1) {
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char c = (char) res;
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if (c == '\r' || c == '\n') {
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position.line += 1;
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position.column = 1;
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} else {
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position.column += 1;
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}
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}
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return res;
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}
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public Position getPosition() {
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return position;
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}
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public Position getPreviousPosition() {
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return previousPosition;
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}
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}
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