%{
    #include <stdio.h>
    extern void yyerror(char*);
%}

%token MEETING LECTURE LAB DONE DATE TIME PLACE
%define parse.error verbose
%start input

%%

input : commands DONE ;

commands : command commands | %empty ;

command : MEETING time_and_place
        | LECTURE time_and_place
        | LAB time_and_place
        ;

time_and_place: DATE TIME TIME PLACE ;

%%

int main() {
    printf("Write a complete input, ending with \"done\" and CTRL-D:\n");
    yyparse();
    printf("Ok!\n");
    return 0;
}

void yyerror(char *s) {
    printf("Incorrect calendar input! Error message: %s\n", s);
}

int yywrap(void) {
    return 1;
}