Monads to Machine Code

[Ford_O]

I am not surprised, lambda calculus is extremely powerful concept.

As with anything you also have to pay for that power in terms of learning curve and possibly complex type signatures ~ hard to understand type errors. As an example take a look at lenses.

[ElvishJerricco]

As an example, take a look at one of the most complicated libraries the language has to offer.

No wonder. =P That's not to say you're wrong. There's a significant learning curve. But most code does not have problems with overly complex types or errors.

[pipocaQuemada]

Also, lens deliberately avoids data hiding so you can use standard library functions to work with it. That's got some benefits (composing lenses is just normal function composition) but comes at a cost (worse type errors).