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1cd376391f
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#include <stdlib.h>
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#include <stdio.h>
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#include "const.h"
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#include "states.h"
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// States of a Turing Machine that checks whether a number DOESN'T divide another number
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// NTS: Check that the first number is smaller? Actually not necessary: see state 2.
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/*
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Initially, I defined a triplet, which was what the different states, which are functions returned.
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typedef struct {
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int state; // Finite list of states: initial (0), state 1, state 2, state 3, ..., state 7.
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int symbol; // Finite list of symbols: 0,1,2,3,4,5,6,7,8,9
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int movement; // Left = -1, Right =1;
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} ssm;
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But I thought that modifying pointers was easier and more elegant.
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*/
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void state0(int *symbol, int *state, int *movement);
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void state1(int *symbol, int *state, int *movement);
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void state2(int *symbol, int *state, int *movement);
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void state3(int *symbol, int *state, int *movement);
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void state4(int *symbol, int *state, int *movement);
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void state5(int *symbol, int *state, int *movement);
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void state6(int *symbol, int *state, int *movement);
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void state7(int *symbol, int *state, int *movement);
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void state8(int *symbol, int *state, int *movement);
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/*void state9(int *symbol, int *state, int *movement);
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void state10(int *symbol, int *state, int *movement);
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*/
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// This function is the delta of which Kozen speaks of in p.210 &ss in Automata and Computability.
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void carry_out_step(int *symbol, int *state, int *movement){ // I could make this a bigger if/else tree, but I don't want to.
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// Initially, I thought to use https://stackoverflow.com/questions/840501/how-do-function-pointers-in-c-work, but this proved unnecessary.
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if(*state==0){
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state0(symbol,state, movement);
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}
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else if(*state==1){
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// Nótese que los else ifs son necesarios, porque después de state0, *state es =1, pero queremos que se de cuenta en la siguiente vuelta
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state1(symbol,state, movement);
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}
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else if(*state==2){
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state2(symbol,state, movement);
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}
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else if(*state==3){
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state3(symbol,state, movement);
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}
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else if(*state==4){
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state4(symbol,state, movement);
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}
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else if(*state==5){
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state5(symbol,state, movement);
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}
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else if(*state==6){
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state6(symbol,state, movement);
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}
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else if(*state==7){
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state7(symbol,state, movement);
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}
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else if(*state==8){
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state8(symbol,state, movement);
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}
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/*
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else if(*state==9){
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state9(symbol,state, movement);
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}
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else if(*state==10){
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state10(symbol,state, movement);
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}
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*/
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}
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void state0(int *symbol, int *state, int *movement){
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if(*symbol ==0){
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*symbol=0; // This is the left endmarker. It isn't changed. This line could be ommited.
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*movement= 1; // Move to the right (0 would be to the left).
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*state=1; // Change to state 1.
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}
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else{
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*state = REJECT; // This is defined as a constant in const.h
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// The program ends, because it has unspecified behaviour
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*movement= 0;
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}
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}
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void state1(int *symbol, int *state, int *movement){
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if(*symbol ==1){
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*symbol=3; // Another symbol.
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*movement= 1; // Move to the right (-1 would be to the left).
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*state=2; // Change to state 2.
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}
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else if(*symbol ==3){ // Note that we need an else because otherwise after it changes a 1 to a 3, symbol=3 and it goes back to state1.
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// Note that we have inadvertently created a function to see whether m is(n't) k modulo n; we would only have to start with n-k 3s at the beginning
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*symbol=3;
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*movement= 1;
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*state=1;
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}
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else if(*symbol ==8){ // 8 = X
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*symbol=8;
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*movement= 1;
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*state=4;
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}
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else{
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*symbol=*symbol;
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*movement= 1;
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*state=1;
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}
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}
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void state2(int *symbol, int *state, int *movement){
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if(*symbol ==2){
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*symbol=4;
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*movement= -1;
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*state=3;
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}
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else if(*symbol ==9){
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*symbol=9;
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*movement= -1;
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*state=7;
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}
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else{
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*symbol=*symbol;
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*movement= 1;
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*state=2;
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}
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}
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void state3(int *symbol, int *state, int *movement){
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if(*symbol ==0){
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*symbol=0;
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*movement= 1;
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*state=1;
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}
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else {
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*symbol=*symbol;
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*movement = -1;
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*state= 3;
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}
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}
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void state4(int *symbol, int *state, int *movement){
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if(*symbol ==2){
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*symbol=4;
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*movement=-1;
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*state=5;
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}
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else if(*symbol ==9){
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*symbol=9;
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*movement=-1; // Only because it rejects
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*state = 6;
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}
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else{
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*symbol = *symbol;
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*movement =1;
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*state=4;
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}
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}
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void state5(int *symbol, int *state, int *movement){
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// Note that after state 4, the TM is in m-territory.
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if(*symbol ==3){
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*symbol=1;
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*movement=-1;
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*state=5;
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}
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else if(*symbol ==5){
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*symbol=6;
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*movement= -1;
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*state = 5;
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}
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else if(*symbol ==0){
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*symbol=0;
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*movement= 1;
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*state = 1;
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}
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else{
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*symbol = *symbol;
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*movement =-1;
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*state=5;
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}
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}
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void state6(int *symbol, int *state, int *movement){
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if(*symbol ==5){
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*symbol=5;
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*movement=0; // Only because it accepts. And it accepts because the first divisor of m is m.
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*state=ACCEPT;
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fprintf(stdout, "\nIt accepts because the first time that n fits in m, it reaches the end of m, so n=m. \n");
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}
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else if(*symbol ==6){
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*symbol=6;
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*movement= 0; // When the function ends, I want it to stay in the same place. But ultimately it doesn't matter.
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*state = REJECT;
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fprintf(stdout, "\nIt rejects because m is bigger than n and n | m.\n");
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}
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else if (*symbol !=6 && *symbol !=5){
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*symbol = *symbol;
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*movement =-1;
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*state=6;
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}
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}
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void state7(int *symbol, int *state, int *movement){
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if(*symbol ==4){
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*symbol=2;
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*movement=-1;
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*state=7;
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}
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else if(*symbol ==3){
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*symbol=1;
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*movement= -1;
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*state = 7;
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}
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else if(*symbol ==6){
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*symbol=5;
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*movement= -1;
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*state = 7;
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}
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else if(*symbol ==0){
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*symbol=0;
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*movement= 1;
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*state = 8;
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}
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else{
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*symbol=*symbol;
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*movement= -1;
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*state = 7;
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}
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}
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void state8(int *symbol, int *state, int *movement){
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if(*symbol ==8){
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*symbol=1;
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*movement=1;
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*state=8;
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}
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else if(*symbol ==7){
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*symbol=8;
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*movement= -1;
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*state = 3;
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}
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else if(*symbol ==2){
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*symbol=2;
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*movement= 0;
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*state = ACCEPT;
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}
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else{
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*symbol=*symbol;
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*movement= 1;
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*state = 8;
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}
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}
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/*
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void state8(int *symbol, int *state, int *movement){
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if(*symbol ==4){
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*symbol=2;
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*movement=-1;
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*state=8;
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}
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else if(*symbol ==3){
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*symbol=1;
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*movement= -1;
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*state = 8;
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}
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else if(*symbol ==0){
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*symbol=0;
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*movement= 1;
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*state = 9;
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}
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else{
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*symbol = *symbol;
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*movement =-1;
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*state=8;
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}
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}
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void state9(int *symbol, int *state, int *movement){
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if(*symbol ==8){
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*symbol=1;
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*movement=1;
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*state=9;
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}
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else if(*symbol ==5){
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*symbol=8;
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*movement= 1;
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*state = 10;
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}
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else if(*symbol ==2){
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*symbol=2;
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*movement= 0; // Only because it accepts
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*state = ACCEPT;
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}
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else if(*symbol ==4){
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*symbol=4;
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*movement= 0; // Only because it accepts
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*state = ACCEPT;
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}
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else{
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*symbol = *symbol;
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*movement =1;
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*state=9;
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}
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}
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void state10(int *symbol, int *state, int *movement){
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if(*symbol ==0){
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*symbol=0;
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*movement=1;
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*state=1;
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}
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else {
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*symbol = *symbol;
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*movement =-1;
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*state=10;
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}
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}*/
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