柔性++不良字符错误等等。刚接触弹性

发布于 2024-12-14 02:00:39 字数 1082 浏览 5 评论 0原文

我们刚刚开始使用 flex 为项目构建词法分析器，但我们不知道如何让它工作。我复制教程中给出的示例代码，并尝试使用 tut 文件作为参数运行 flex++，但每次都收到错误。例如

输入文件 (calc.l)

%name Scanner
%define IOSTREAM

DIGIT   [0-9]
DIGIT1  [1-9]

%%

"+"               { cout << "operator <" << yytext[0] << ">" << endl; }
"-"               { cout << "operator <" << yytext[0] << ">" << endl; }
"="               { cout << "operator <" << yytext[0] << ">" << endl; }
{DIGIT1}{DIGIT}*  { cout << "  number <" << yytext    << ">" << endl; }
.                 { cout << " UNKNOWN <" << yytext[0] << ">" << endl; }

%%

int main(int argc, char ** argv)
{
    Scanner scanner;
    scanner.yylex();
    return 0;
}

与我得到的代码

flex++ calc.l
calc.l:1: 错误字符: % calc.l:1: 未知错误处理部分 1
calc.l:1: 未知错误处理部分 1
calc.l:1: 未知错误处理部分 1
calc.l:2: 无法识别的“%”指令

任何人都可以帮助我理解我在这里做错了什么吗？干杯

原文

we are just getting started using flex to build a lexer for a project, but we cant figure out how to get it to work. I copy the example code given in tutorials and try to run flex++ with the tut file as its argument however I just receive an error each time. e.g.

input file (calc.l)

%name Scanner
%define IOSTREAM

DIGIT   [0-9]
DIGIT1  [1-9]

%%

"+"               { cout << "operator <" << yytext[0] << ">" << endl; }
"-"               { cout << "operator <" << yytext[0] << ">" << endl; }
"="               { cout << "operator <" << yytext[0] << ">" << endl; }
{DIGIT1}{DIGIT}*  { cout << "  number <" << yytext    << ">" << endl; }
.                 { cout << " UNKNOWN <" << yytext[0] << ">" << endl; }

%%

int main(int argc, char ** argv)
{
    Scanner scanner;
    scanner.yylex();
    return 0;
}

with this code i get

flex++ calc.l
calc.l:1: bad character: %
calc.l:1: unknown error processing section 1
calc.l:1: unknown error processing section 1
calc.l:1: unknown error processing section 1
calc.l:2: unrecognised '%' directive

could anyone help me understand what im doing wrong here? cheers

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妄司 2024-12-21 02:00:39

您可以尝试以下操作：

将 %{ ... %} 添加到文件的前几行，
添加 #include 和 using namespace std; （而不是尝试定义扫描仪）
仅
使用 yylex( ) （而不是尝试调用不存在的扫描仪的方法）

对于您的示例，它可能看起来像这样：

%{
#include <iostream>
using namespace std;
%}

DIGIT   [0-9]
DIGIT1  [1-9]

/* read only one input file */
%option noyywrap

%%
"+"               { cout << "operator <" << yytext[0] << ">" << endl; }
"-"               { cout << "operator <" << yytext[0] << ">" << endl; }
"="               { cout << "operator <" << yytext[0] << ">" << endl; }
{DIGIT1}{DIGIT}*  { cout << "  number <" << yytext    << ">" << endl; }
.                 { cout << " UNKNOWN <" << yytext[0] << ">" << endl; }
%%

int main(int argc, char** argv)
{
    yylex();
    return 0;
}

You might try something like:

adding %{ ... %} to the first couple of lines in your file
adding #include <iostream> and using namespace std; (instead of trying to define Scanner)
adding %option noyywrap above the rules section
using just yylex() (instead of trying to call the method of a non-existant Scanner)

With your example, it could look something like this:

%{
#include <iostream>
using namespace std;
%}

DIGIT   [0-9]
DIGIT1  [1-9]

/* read only one input file */
%option noyywrap

%%
"+"               { cout << "operator <" << yytext[0] << ">" << endl; }
"-"               { cout << "operator <" << yytext[0] << ">" << endl; }
"="               { cout << "operator <" << yytext[0] << ">" << endl; }
{DIGIT1}{DIGIT}*  { cout << "  number <" << yytext    << ">" << endl; }
.                 { cout << " UNKNOWN <" << yytext[0] << ">" << endl; }
%%

int main(int argc, char** argv)
{
    yylex();
    return 0;
}

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