%%

[t]+

is   |

am   |

are  |

was  |

were {printf("%s: is a verb",yytext);}

[a-zA-Z]+ {printf("%s: is a verb",yytext);}

. |n

%%

int main(int argc, char *argv[]){
    yyin = fopen(argv[1], "r");
    yylex();
    fclose(yyin);
}

%option noyywrap
%x COMMENT_SINGLE
%x COMMENT_MULTI

%top{
/* for strndup */
#include <string.h>
}

%{
char* commentStart;
%}

%%

[ntr ]+ {
  /* ignore whitespace */ }

<INITIAL>"//" {
  /* begin of single-line comment */
  commentStart = yytext;
  BEGIN(COMMENT_SINGLE);
}

<COMMENT_SINGLE>n {
  /* end of single-line comment */
  char* comment = strndup(commentStart, yytext - commentStart);
  printf("'%s': was a single-line commentn", comment);
  free(comment);
  BEGIN(INITIAL);
}

<COMMENT_SINGLE>[^n]+ {
  /* suppress whatever is in the comment */
}

<INITIAL>"/*" {
  /* begin of multi-line comment */
  commentStart = yytext;
  BEGIN(COMMENT_MULTI);
}

<COMMENT_MULTI>"*/" {
  /* end of multi-line comment */
  char* comment = strndup(commentStart, yytext + 2 - commentStart);
  printf("'%s': was a multi-line commentn", comment);
  free(comment);
  BEGIN(INITIAL);
}

<COMMENT_MULTI>. {
  /* suppress whatever is in the comment */
}

<COMMENT_MULTI>n {
  /* don't print newlines */
}

is   |
am   |
are  |
was  |
were {
  printf("'%s': is a verbn", yytext);
}

[a-zA-Z]+ {
  printf("'%s': is not a verbn", yytext);
}

. {
  /* don't print everything else */
}

%%

int main(int argc, char *argv[]){
  yyin = fopen(argv[1], "r");
  yylex();
  fclose(yyin);
}