JavaCUPCUP 解析器生成器

JavaCUP 是 Java 語言實(shí)現(xiàn)的 CUP 解析器生成器。

示例代碼：

// 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;
      }
    }
};