Question

我有以下.flex文件：

package mini_c;

import java_cup.runtime.*;
import static mini_c.sym.*;

%%

%class Lexer
%unicode            /* The characters are unicode */
%cup                /* Syntax analyser with cup (Parser part) */
%cupdebug           /* ? */
%line               /* Decompose by line */
%column             /* Decompose by column */
// %yylexthrow Exception        /* Can throw exceptions */

%{
    /* No need for preamble in JAVA */
%}

WhiteSpace  = [ \t\r\n]+
Integer     = [:digit:]+    // Digit is defined on jflex
Identifier  = ([:jletter:] | [_]) ([:jletter:] | [:digit:] | [_] )* // Will be used to read function names

%%
<YYINITIAL> {
    "(" { return new Symbol(LPAR, yyline, yycolumn); }
    ")" { return new Symbol(RPAR, yyline, yycolumn); }
    "{"
        { return new Symbol(LB, yyline, yycolumn); }
    "}" { return new Symbol(RB, yyline, yycolumn); }
    ";" { return new Symbol(SEMICOLON, yyline, yycolumn);}
    "return"
        { return new Symbol(RETURN, yyline, yycolumn); }
    {Integer}
        { return new Symbol(CST, yyline, yycolumn, Integer.parseInt(yytext())); }
    {Identifier}
        { return new Symbol(IDENT, yyline, yycolumn, yytext()); }
    .   { throw new Exception(String.format("Error in line %d, column %d: illegal character '%s'\n", yyline, yycolumn, yytexy())); }
}

当我写jflex Lexer.flex时（Lexer.flex显然是文件的名称） cmd上显示以下内容：

Reading "Lexer.flex"

Warning : Macro "WhiteSpace" has been declared but never used.
Constructing NFA : 31 states in NFA
Converting NFA to DFA :
................
18 states before minimization, 15 states in minimized DFA
Old file "Lexer.java" saved as "Lexer.java~"
Writing code to "Lexer.java"
Error: Syntax error @ Symbol: ID (unknown:4/15 - unknown:4/20)
Error : Illegal use of reserved word
Warning : Scanner at 6(1): Unrecognized character '%' -- ignored
Warning : Scanner at 6(2): Unrecognized character '%' -- ignored
Warning : Scanner at 8(1): Unrecognized character '%' -- ignored
Error: Syntax error @ Symbol: ID (unknown:8/2 - unknown:8/6)
Warning : Scanner at 9(1): Unrecognized character '%' -- ignored
Warning : Scanner at 10(1): Unrecognized character '%' -- ignored
Warning : Scanner at 11(1): Unrecognized character '%' -- ignored
Warning : Scanner at 12(1): Unrecognized character '%' -- ignored
Warning : Scanner at 13(1): Unrecognized character '%' -- ignored
Warning : Scanner at 16(1): Unrecognized character '%' -- ignored
Warning : Scanner at 16(2): Unrecognized character '{' -- ignored
Warning : Scanner at 18(1): Unrecognized character '%' -- ignored
Warning : Scanner at 18(2): Unrecognized character '}' -- ignored
Warning : Scanner at 20(12): Unrecognized character '=' -- ignored
Warning : Scanner at 20(16): Unrecognized character '\' -- ignored

cmd错误实际上更长，但我想你明白了。

在“简单示例”部分下尝试制作http://jflex.de/manual.html#Example时。我复制粘贴示例，出现以下错误：

Reading "Lexer.flex"

Error in file "Lexer.flex" (line 87):
This seems not to be a lexical specification (first %% is missing)
                                                        yytext()+">"); }
1 error, 0 warnings.
Warning : Scanner at 7(5): Unrecognized character '%' -- ignored
Warning : Scanner at 7(6): Unrecognized character '%' -- ignored
Warning : Scanner at 9(5): Unrecognized character '%' -- ignored
Error: Syntax error @ Symbol: ID (unknown:9/6 - unknown:9/10)
Warning : Scanner at 10(5): Unrecognized character '%' -- ignored
Warning : Scanner at 11(5): Unrecognized character '%' -- ignored

谢谢！

Answer 1

解决！我的jflex.bat文件出现问题。有效的好方法就是这一行：

select
    case col
        when 'a' then 'foo'
        when 'b' then 'bar'
        when 'c' then 'baz'
        else null 
    end as col
from t

我的拼写错误，是jflex-1.6.jar

JFLEX错误：语法错误@符号：ID（...）错误：非法使用保留字

1 个答案: