如何使用 .flex 文件解决此语法问题？

Question

我是第一次使用 jflex，我正在按照我在互联网上找到的母语（葡萄牙语）教程进行安装和组装。

但是当我尝试生成“Lexer”类时，它在我的“.flex”文件中显示语法错误，我不知道会发生什么，因为一切似乎都正常。

.flex 文件

//NOME_VARIAVEL,INT,DEC,COMENTARIO,BRANCO,PALAVRA_CHAVE,ERRO
package Compilador;
import static Compilador.Token.*;
%%
%{
    private void imprimir (String token,String lexema){
            System.out.println(lexema +" ===>> " + token);
    }
%}
%class Lexer
%type Token
nomeVariavel = [_a-zA-Z][_zA-z0-9]*
inteiro = [0-9]+
decimal = [0-9]+["."]+[0-9]+
blocoComentario = "/*" ~"*/"
branco = [\t|\n|\r]+
linhaComentario = [branco]*"//" .*
palavrasChave = "if" | "class" | "int" | "while" | "for" | "do" | "float"
%%

{palavrasChave}     { imprimir("PALAVRA_CHAVE : ", yytext()); return PALAVRA_CHAVE;  } 
{nomeVariavel}      { imprimir("VARIAVEL : ", yytext()); return NOME_VARIAVEL;  }
{inteiro}           { imprimir("NUMERO INTEIRO : ", yytext()); return INT;  }
{decimal}           { imprimir("NUMERO DECIMAL : ", yytext()); return DEC;  }
{blocoComentario}   { imprimir("COMENTARIO : ", yytext()); return COMENTARIO;    }
{linhaComentario}   { imprimir("COMENTARIO : ", yytext()); return COMENTARIO; }
{branco}            ( return BRANCO; } 
.   {imprimir("<<< CARACTER INVALIDO!!! >>>   ",yytext()); return ERROR;}
<<EOF>>     {return null;}

Token.java 文件

package compilador;
public enum Token{
   NOME_VARIAVEL, INT, DEC, COMENTARIO, BRANCO, PALAVRA_CHAVE, ERROR;

}

generator.flex 文件

package compilador;

import java.io.*;

public class GeraLexer {
    public static void main(String[] args) throws IOException  {
     String arquivo ="<path redacted for reasons, but it is finding the file>";
     geraLexer(arquivo);
    }

    public static void geraLexer(String arq){
        File file = new File(arq);
        jflex.Main.generate(file);
    }
}

生成时出现错误

Reading "<path redacted for reasons, but it is finding the file>"

Error in file "<path redacted for reasons, but it is finding the file>" (line 28): 
Syntax error.
.   {imprimir("<<< CARACTER INVALIDO!!! >>>   ",yytext()); return ERROR;}
 ^
Exception in thread "main" jflex.GeneratorException: Generation aborted
    at jflex.Main.generate(Main.java:139)
    at compilador.GeraLexer.geraLexer(GeraLexer.java:13)
    at compilador.GeraLexer.main(GeraLexer.java:8)
Java Result: 1
CONSTRUÍDO COM SUCESSO (tempo total: 0 segundos)

感谢任何愿意提供帮助的人，是的，我先用谷歌搜索了。

Answer 1

在上一行中，你有

{branco}            ( return BRANCO; } 

( 应该是 {。

您很快就会发现编写自己的解析器，在正确的位置发现错误并不总是那么容易。检测到错误的时间通常比您想要的晚一个标记，有时该标记位于下一行。