Lex输入文件，将C语言中注释之外的保留字转换为大写。习题2.23

upper-keyword.lex

%option noyywrap

types      auto|enum|unsigned|void|float|short|volatile|char|signed|const|int|double|long
control    break|return|case|for|while|goto|continue|if|do|switch|else
other      extern|sizeof|static|default|struct|typedef|register|union
keywords    {types}|{control}|{other}

prefix      [ \,\;\{\}\(\)\t\n\#]
suffix      [ \,\;\{\}\(\)\t\n\:\*]

/*
prefix      [^a-zA-Z0-9_]
suffix      [^a-zA-Z0-9_]
*/

/*
%{
    int inComment = 0;
%}
*/


%%


"/*"      ECHO;{
    register int c,prev_c;
    //inComment = 1;
    for ( ; ; ){
        while ( (c = input()) != '*' && c != EOF ){
            printf("%c",c);    
        }
                   
        if ( c == '*' ){
            printf("%c",c);
            prev_c = c;
            while ( prev_c == '*' && (c = input()) != '/' ){
                printf("%c",c);
                prev_c = c;
                break;
            }
                       
                       
            if ( c == '/' ){
                printf("/");
                //inComment = 0;
                break;    /* found the end */
            }
        }
                   
        if ( c == EOF ){
            error( "EOF in comment" );
            break;
        }
    }
}
 
"//"   ECHO;{
    register int c;
    //inComment = 1;
    for ( ; ; ){
        while ( (c = input()) != '\n' && c != EOF ){
            printf("%c",c); 
        }
        if(c == '\n'){
            printf("\n");
            //inComment = 0;
            break;
        }
        if ( c == EOF ) {
            error( "EOF in comment" );
            break;
        }
    }
}



{prefix}{keywords}/{suffix}   |
^{keywords}/{suffix}          { 
                                 while(*yytext != '\0'){
                                     printf("%c",toupper(*yytext++));

                                 }
                           }


%%
void main(){
    yylex();
}