c - Brainf**k interpreter problems -


i'm new c. i'm trying write brainfuck interpreter. have tried far.

#include <unistd.h> #include <stdlib.h>  char    *line; int     curr_pos;  void    interprete(char *coms) {     int a;     int curr_loop;      = -1;     curr_loop = 0;     while (line[++a])         line[a] = 0;     = -1;     while (coms[++a])     {         if (coms[a] == '+')             line[curr_pos]++;         else if (coms[a] == '-')             line[curr_pos]--;         else if (coms[a] == '>')             curr_pos++;         else if (coms[a] == '<')             curr_pos--;         else if (coms[a] == '.')             write(1, &line[curr_pos], 1);         else if (coms[a] == '[')         {             if (line[curr_pos])                 curr_pos++;             else             {                 curr_loop = 1;                 while (curr_loop)                 {                     ++a;                     if (coms[a] == '[')                         curr_loop++;                     else if (coms[a] == ']')                         curr_loop--;                 }             }         }         else if (coms[a] == ']')         {             if (line[curr_pos])             {                 curr_loop = 1;                 while (curr_loop)                 {                     --a;                     if (coms[a] == '[')                         curr_loop--;                     else if (coms[a] == ']')                         curr_loop++;                 }             }             else                 curr_pos++;         }     } }  int main(int ac, char **av) {     if (ac == 2)     {         curr_pos = 0;         line = malloc(sizeof(char) * 4096);         interprete(av[1]);     }     write(1, "\n", 1); }

it works without loops ("[" , "]").when try "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>."

it gives me output 

^b^a^h^h^k^b^q^k^n^h^@^c^@

expected output:

hello world!

i guess problems in following code-blocks:

else if (coms[a] == '[') {     ... } else if (coms[a] == ']') {     ... }

the program looking other bracket (and finds it), code-pointer additionally incremented in while-statement (line 17). have decrement a 1 after search-loops. second problem is, increment data-pointer (curr_pos)
if com[a] == '[' , line[curr_pos] != 0
and if com[a] == ']' , line[curr_pos] == 0
you have increment code-pointer (a) still automatically incremented in while-statement. have pass in case. finally, don't have check @ both brackets if current cells value unequal zero. suggested code this:

else if (coms[a] == '[') {     if (!line[curr_pos])     {         curr_loop = 1;         while (curr_loop)         {             ++a;             if (coms[a] == '[')                 cur_loop++;             else if (coms[a] == ']')                 cur_loop--;         }         a--;     } } else if (coms[a] == ']') {     // can jump opening bracket '['     // because program checks again , jumps behind     // closing bracket if line[a] != 0     curr_loop = 1;     while (curr_loop)     {         --a;         if (coms[a] == '[')             curr_loop--;         else if (coms[a] == ']')             curr_loop++;     }     a--; }

by way: try implement ','-command. makes brainfuck programs way more interesting ;)


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