Flex++ bad character error and more. new to flex

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. eg

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


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;
    }
    

    What is the version of flex++ you using? I uses 'Function: fast lexical analyzer generator C/C++ V2.3.8-7 (flex++), based on 2.3.8 and modified by coetmeur@icdc.fr for c++' (-? option) and your cacl.c is processed perfectly..

    For Win32, this version of Flex++/Bison++ is here

    链接地址: http://www.djcxy.com/p/9922.html

    上一篇: 在Symfony2中创建组合的客户端和服务器端验证

    下一篇: Flex ++糟糕的字符错误等等。 新的flex