%{/* * We now build a lexical analyzer to be used by a higher-level parser. */#include "ch1-06y.h"	/* token codes from the parser */#define LOOKUP 0 /* default - not a defined word type. */int state; %}%%\n	{ state = LOOKUP; }\.\n	{	state = LOOKUP;		return 0; /* end of sentence */	}^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);		  /* don't return, just ignore it */		}            }          }.	; %%/* define a linked list of words and types */struct word {	char *word_name;	int word_type;	struct word *next;};struct word *word_list; /* first element in word list */extern void *malloc();intadd_word(int type, char *word){	struct word *wp;		if(lookup_word(word) != LOOKUP) {		printf("!!! warning: word %s already defined \n", word);		return 0;	}		/* word not there, allocate a new entry and link it on the list */	wp = (struct word *) malloc(sizeof(struct word));	wp->next = word_list;	/* have to copy the word itself as well */		wp->word_name = (char *) malloc(strlen(word)+1);	strcpy(wp->word_name, word);	wp->word_type = type;	word_list = wp;	return 1;	/* it worked */}intlookup_word(char *word){	struct word *wp = word_list;	/* search down the list looking for the word */	for(; wp; wp = wp->next) {		if(strcmp(wp->word_name, word) == 0)			return wp->word_type;	}	return LOOKUP;	/* not found */}