Fossil

  int base = 10;
  int (*isdigit)(char) = th_isdigit;

  if( n<0 ){
    n = th_strlen(z);
  }

  if( n>0 && (z[0]=='-' || z[0]=='+') ){
    i = 1;
  }
  if( n>2 ){
    if( z[i]=='0' ){
      if( z[i+1]=='x' || z[i+1]=='X' ){
        i += 2;
        base = 16;
        isdigit = th_ishexdig;
      }else if( z[i+1]=='o' || z[i+1]=='O' ){
        i += 2;
        base = 8;
        isdigit = th_isoctdig;
      }else if( z[i+1]=='b' || z[i+1]=='B' ){
        i += 2;
        base = 2;
        isdigit = th_isbindig;
      }
    }
  }
  for(; i<n; i++){
    char c = z[i];
    if( !isdigit(c) ){
      Th_ErrorMessage(interp, "expected integer, got: \"", z, n);
      return TH_ERROR;