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94 lines
2.1 KiB
C
94 lines
2.1 KiB
C
#include <stdio.h>
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#define TAPE_SIZE 80
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#define RULES_SIZE 256
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typedef struct {
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char state; /* current state */
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char symbol; /* current symbol */
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int head; /* index of head */
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char tape[TAPE_SIZE]; /* tape of characters */
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int nrules; /* number of rules */
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/* state, symbol, new state, new symbol, direction (even right, odd left ) */
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char rules[RULES_SIZE][5];
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} Machine;
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Machine m;
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int nsteps;
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int main(int argc, char *argv[]){
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int i,n=0;
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FILE *f;
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if(!(f = fopen(argv[1], "r"))){
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fprintf(stderr, "failed to load file\n");
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return 1;
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}
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printf("%s\n\n", argv[1]);
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/* read machine description */
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printf("initial state: ");
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fscanf(f,"%c",&m.state);
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printf("%c\n",m.state);
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printf("initial tape: ");
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fscanf(f,"%s",m.tape);
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printf("%s\n",m.tape);
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printf("initial position of head: ");
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fscanf(f,"%d",&m.head);
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m.head = (m.head+TAPE_SIZE)%TAPE_SIZE;
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printf("%d\n",m.head);
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printf("number of rules: ");
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fscanf(f,"%d",&m.nrules);
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printf("%d\n",m.nrules);
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for(i=0; i<m.nrules; i++){
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printf("rule number %d: ",i);
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fscanf(f,"%s",m.rules[i]);
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printf("%s\n",m.rules[i]);
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}
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printf("max number of simulation steps: ");
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fscanf(f,"%d",&nsteps);
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printf("%d\n\n",nsteps);
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/* simulate */
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int irules; /* rules index */
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do{
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printf("step %d\n",n);
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/* print head and state */
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for(i=0; i<m.head; i++)
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printf(" ");
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printf("%c\n",m.state);
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/* print tape: */
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printf("%s\n",m.tape);
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/* get symbol at head position */
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m.symbol = m.tape[ m.head ];
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/* search for corresponding rule */
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irules = -1;
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for(i=0; i<m.nrules && irules<0; i++)
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if(m.rules[i][0] == m.state && m.rules[i][1] == m.symbol)
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irules = i;
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if( irules == -1) /* halt if not found */
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printf("halted\n");
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else{ /* update machine otherwise */
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m.state = m.rules[irules][2]; /* new state */
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m.tape[ m.head ] = m.rules[irules][3]; /* new symbol */
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/* move head */
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if( m.rules[irules][4]%2 ) /* if odd, move to left */
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m.head = (m.head-1+TAPE_SIZE)%TAPE_SIZE;
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else /* if even, move to right */
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m.head = (m.head+1)%TAPE_SIZE;
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}
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printf("\n");
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}while( ++n<nsteps && irules != -1);
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return 0;
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}
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