Hi,

This is the first book that has truly helped to learn Haskell and to develop confidence to write programs in this language. Thanks so much.

I have some feedback about Chapter 10. In the “Building a Basic Metrics System with IORefs” section, I can’t replicate the space leak problems related to the histogram. The timeFunction always ends up measuring zero for every function that I’m capturing metrics for:

The memory usage report doesn’t correlate to the number of files that the application is reading either. I acknowledge that every computer environment is different and that may be the cause for my results. Nevertheless, it would be easier to follow the chapter if I could reproduce the memory leak in my local environment.

A smaller observation is that the displayMetrics function isn’t implemented in the chapter although it is referenced in the code examples. Implementing this function is easy, nevertheless, I thought it might be worth mentioning.

Thanks again for writing this book