JavaCUPCUP 解析器生成器

JavaCUP 是 Java 语言实现的 CUP 解析器生成器。

示例代码：

// Simple Example Scanner Class 

// scanner.java

import java_cup.runtime.*;

import java.io.*;

//import sym;



public class scanner implements java_cup.runtime.Scanner {

  /* single lookahead character */

  protected static int next_char;

  // since cup v11 we use SymbolFactories rather than Symbols

  private SymbolFactory sf = new DefaultSymbolFactory();

  private static FileReader fileReader;

  public scanner(FileReader fr){

      this.fileReader=fr;

  }

  /* advance input by one character */

  protected static void  advance()

    throws java.io.IOException

    { next_char = fileReader.read(); }



  /* initialize the scanner */

  public static void init()

    throws java.io.IOException

    { advance(); }



  /* recognize and return the next complete token */

  public Symbol next_token()

    throws java.io.IOException

    {

      for (;;)

        switch (next_char)

      {

        case '0': case '1': case '2': case '3': case '4': 

        case '5': case '6': case '7': case '8': case '9': 

          /* parse a decimal integer */

          int i_val = 0;

          do {

            i_val = i_val * 10 + (next_char - '0');

            advance();

          } while (next_char >= '0' && next_char <= '9');

        return sf.newSymbol("NUMBER",sym.NUMBER, new Integer(i_val));



        case ';': advance(); return sf.newSymbol("SEMI",sym.SEMI);

        case '+': advance(); return sf.newSymbol("PLUS",sym.PLUS);

        case '-': advance(); return sf.newSymbol("MINUS",sym.MINUS);

        case '*': advance(); return sf.newSymbol("TIMES",sym.TIMES);

        case '/': advance(); return sf.newSymbol("DIVIDE",sym.DIVIDE);

        case '%': advance(); return sf.newSymbol("MOD",sym.MOD);

        case '(': advance(); return sf.newSymbol("LPAREN",sym.LPAREN);

        case ')': advance(); return sf.newSymbol("RPAREN",sym.RPAREN);



        case -1: return sf.newSymbol("EOF",sym.EOF);



        default: 

          /* in this simple scanner we just ignore everything else */

          advance();

        break;

      }

    }

};