JavaCUP CUP 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;
}
}
};