anchor.diff:  assert(inform_succeeded(&err));
   // ce == 0.507757
   ----
  +[horizontal]
  +Header:: `inform/conditional_entropy.h`
   ****
   
   ****
  
positive.code: // no need to free since `h` was statically allocated in this scope
  // free(h);
  ----
  ****
  
  [[conditional-entropy]]
  
negative.code:         size_t m, int b, size_t kpast, size_t kfuture, double *pi,
          inform_error *err);
  ----
  [horizontal]
  Header:: `inform/predictive_info.h`
  ****
  
  [[relative-entropy]]
  