[질문] flex와 bison 관련 질문입니다.

%{
#include "example.tab.h"
#define LOOKUP 0
int state;
%}
 
%%
\n	{ state=LOOKUP;}
\.\n	{ 
		state=LOOKUP; 
		return 0;
	}
^verb	{ state=VERB; }
^adj	{ state=ADJECTIVE; } 
^adv	{ state=ADVERB; }
^noun	{ state=NOUN; }
^prep	{ state=PREPOSITION; }
^pron	{ state=PRONOUN; }
^conj	{ state=CONJUNCTION; } 
[a-zA-Z]+ {
	if(state !=LOOKUP) {
		 add_word(state, yytext);
 
	} else {
		switch(lookup_word(yytext)) {
		case VERB: 		
			return(VERB);
		case ADJECTIVE: 	
			return(ADJECTIVE);
		case ADVERB:		
			return(ADVERB);
		case NOUN:		
			return(NOUN);
		case PREPOSITION: 	
			return(PREPOSITION);
		case PRONOUN:		
			return(PRONOUN);
		case CONJUNCTION: 	
			return(CONJUNCTION);
		default:
			printf("%s: don't recognize\n", yytext);
		}
	}
}
 
\. ;
%%
 
struct word {
	char *word_name;
	int word_type;
	struct word *next;
};
 
struct word *word_list;
extern void *malloc();
 
int 
add_word(int type, char *word)
{
	struct word *wp;
	if(lookup_word(word) != LOOKUP) {
		printf("!!! warning: word %s already defined \n", word);
		return 0;
	}
 
	wp = (struct word*) malloc(sizeof(struct word));
	wp->next = word_list;
 
	wp->word_name = (char*) malloc(strlen(word)+1);
	strcpy(wp->word_name, word);
	wp->word_type = type;
	word_list = wp;
	return 1;
}
 
int 
lookup_word(char *word)
{
	struct word *wp=word_list;
 
	for(; wp; wp->next) {
		if(strcmp(wp->word_name, word) ==0)
			return wp->word_type;
	}
	return LOOKUP;
}

%{
#include<stdio.h>
%}
%token NOUN PRONOUN VERB ADVERB ADJECTIVE PREPOSITION CONJUNCTION
%%
sentence: subject VERB object { printf("Sentence is valid.\n"); }
  ;}
subject:  NOUN
  | PRONOUN
  ;
object:  NOUN
  ;
%%
 
 
extern FILE *yyin;
main()
{
	do
	{
		yyparse();
	}while(!feof(yyin));
}
yyerror(s)
char *s;
{
	fprintf(stderr, "%s\n",s);
}