/*
 *	minervini@neuralnoise.com 2004
 *	automa per riconoscere le stringhe con #(a) dispari e #(b) pari (in teoria);
 *
 *	X = { a, b }
 *  M = (Q, delta, Q0, F)
 *  Q = { Q0, Q1, Q2, Q3 }
 *  F = { Q1 }
 *  delta Q0 Q1 Q2 Q3
 *  -------------------
 *    a   Q1 Q0 Q3 Q2  
 *    b   Q2 Q3 Q0 Q1
 */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

#ifndef MAXTOKEN
	#define MAXTOKEN 256
#endif

#define Q0 1
#define Q1 2
#define Q2 3
#define Q3 4

struct token {
	char name[MAXTOKEN + 1];
	unsigned char stato;
};

int gettoken (FILE *src, struct token *tkn, int max) {

	int car, i = 0;
	tkn->stato = 1;

	if ((car = getc(src)) != EOF) {
		
		while (isspace(car))
			car = getc(src);

		while (car != EOF && !isspace(car) && i <= max) {
			
			switch (car) {
			case 'a':
				switch (tkn->stato) {
				case Q0:
					tkn->stato = Q1;
					break;
				case Q1:
					tkn->stato = Q0;
					break;
				case Q2:
					tkn->stato = Q3;
					break;
				case Q3:
					tkn->stato = Q2;
					break;
				default:
					tkn->stato = 0;
					break;
				}
			break;
			case 'b':
				switch (tkn->stato) {
				case Q0:
					tkn->stato = Q2;
					break;
				case Q1:
					tkn->stato = Q3;
					break;
				case Q2:
					tkn->stato = Q0;
					break;
				case Q3:
					tkn->stato = Q1;
					break;
				default:
					tkn->stato = 0;
					break;
				}
			break;
			}
			tkn->name[i] = car;
			i++;
			car = getc(src);
		}

		tkn->name[i] = 0;
		
		return(1);
	} else {
		return(0);
	}
}

int main () {

	FILE *source;
	char *categories[] = { "non valido", "A pari B pari", "A dispari B pari (finale)", "A pari B dispari", "A dispari B dispari" };
	struct token next;

	source = fopen("source.txt", "r");

	while (gettoken(source, &next, MAXTOKEN))
		printf("token: %s -> %s\n", next.name, categories[next.stato]);

	fclose(source);
	return(0);
}