anchor.diff:  int const series[18] = {0,0,1,1,1,1,0,0,0,
                           1,0,0,1,0,0,1,0,0};
   double ai[14];
  -inform_local_active_info(series, 1, 9, 2, 2, ai, &err);
  +inform_local_active_info(series, 2, 9, 2, 2, ai, &err);
   assert(inform_succeeded(&err));
   // ai ~ { 0.807, -0.363, 0.637, 0.637, -0.778, 0.807, -1.193,
   //        0.807,  0.807, 0.222, 0.807,  0.807, 0.222,  0.807 }
  
positive.code: 
  [[block-entropy]]
  == Block Entropy
  
  ****
  [[inform_block_entropy]]
  
negative.code: ----
  double *inform_local_block_entropy(int const *series, size_t n,
          size_t m, int b, size_t k, double *ent, inform_error *err);
  ----
  Compute the local block entropy of a time series with block size `k`.
  
  *Examples:*
  
  One initial condition:
  [source,c]
  ----
  inform_error err = INFORM_SUCCESS;
  int const series[9] = {0,0,1,1,1,1,0,0,0};
  
  // k == 1
  double *h = inform_local_block_entropy(series, 1, 9, 2, 1, NULL, &err);
  assert(inform_succeeded(&err));
  // h ~ { 0.848, 0.848, 1.170, 1.170, 1.170, 1.170, 0.848, 0.848, 0.848 }
  
  // k == 2
  double *h = inform_local_block_entropy(series, 1, 9, 2, 2, NULL, &err);
  assert(inform_succeeded(&err));
  // h ~ { 1.415, 3.000, 1.415, 1.415, 1.415, 3.000, 1.415, 1.415 }
  
  free(ai);
  ----
  
  Two initial conditions:
  [source,c]
  ----
  inform_error err = INFORM_SUCCESS;
  int const series[18] = {0,0,1,1,1,1,0,0,0,
                          1,0,0,1,0,0,1,0,0};
  double h[16];
  inform_local_block_entropy(series, 2, 9, 2, 2, h, &err);
  assert(inform_succeeded(&err));
  // h ~ { 1.415, 2.415, 2.415, 2.415, 2.415, 2.000, 1.415, 1.415,
  //       2.000, 1.415, 2.415, 2.000, 1.415, 2.415, 2.000, 1.415 }
  
  // no need to free since `h` was statically allocated in this scope
  // free(h);
  ----
  ****
  
  