gistfile1.m

#import <Foundation/Foundation.h>

#define TAPE_MAX_WIDTH 1

@interface BrainFxck : NSObject
{
  const char    *code;
  unsigned char *tape;
  unsigned int  position;
  unsigned int  tape_width;
  NSMutableString *trace;
}

@property (readonly) NSMutableString *trace;

- (void)evalCode:(NSString*)code;
- (void)reallocTape;
- (NSString*)trace;
@end

@implementation BrainFxck

@synthesize trace;

- (id)init
{
  tape = calloc(TAPE_MAX_WIDTH, sizeof(unsigned char));
  tape_width = TAPE_MAX_WIDTH;
  trace = [NSMutableString new];

  return self;
}

- (void)evalCode:(NSString*)codeString
{
  code = [codeString cStringUsingEncoding:NSUTF8StringEncoding];

  while(*code)
  {
    switch(*code)
    {
      case '+':
        tape[position]++;
        break;
      case '-':
        tape[position]--;
        break;
      case '>':
        position++;
        if(position == tape_width) [self reallocTape];
        break;
      case '<':
        position--;
        break;
      case '[':
        if(tape[position] == 0) {
          while(*code != ']') code++;
        }
        break;
      case ']':
        if(tape[position] != 0) {
          while(*code != '[') code--;
        }
        break;
      case '.':
        printf("%c", tape[position]);
        break;
      default:
        code++;
        continue;
    }

    // Trace status
    [trace appendFormat:@"%c(%03d)", *code, position];
    for(int n = 0; n < tape_width; n++)
    {
      [trace appendFormat:@"|%03d", tape[n]];
    }
    [trace appendString:@"|\n"];

    code++;
  }
}

- (void)reallocTape
{
  unsigned int new_tape_width = tape_width + TAPE_MAX_WIDTH;

  realloc(tape, sizeof(unsigned char) * new_tape_width);

  for(int n = tape_width; n < new_tape_width; n++)
  {
    tape[n] = 0;
  }

  tape_width += TAPE_MAX_WIDTH;
}

- (void)dealloc
{
  free(tape);
  [trace release];
  [super dealloc];
}
@end

int main(int argc, char **argv)
{
  NSAutoreleasePool *pool = [NSAutoreleasePool new];

  BrainFxck *bf = [[BrainFxck new] autorelease];

  [bf evalCode:
    @"++++++ [> ++++++++++ < -] > +++++ ."
    @"> ++++++++++ ."
  ];

  NSLog(@"%@", bf.trace);

  [pool release];

  return 0;
}