As a person who loves Haskell, I generally agree. Because it's about as declarative as you can get, you have no insight into the execution model. In particularl

As a person who loves Haskell, I generally agree. Because it's about as declarative as you can get, you have no insight into the execution model. In particularly, following the lazy/strict chain is hard (it's occasionally hard, especially in multithreaded scenarios to know what statement will be fully evaluated, or just "thunk"). The hope is, of course, that the compiler will get so good that it can leverage the purity of the code to do what you want as fast as possible (it's a throughput language after all). Note, however, that Haskell can easily solve the problem mentioned in this article, and you have several ways of doing it.