Забавно, как ленивость не вошла в мозг даже авторам realworldhaskell.
> Note, though, that the chain is not completely short-circuited. Each (>>=) or (>>) in the chain will still match a Nothing on its left, and produce a Nothing on its right, all the way to the end. It's easy to forget this point: when a computation in the chain fails, the subsequent production, chaining, and consumption of Nothing values is cheap at runtime, but it's not free.
http://book.realworldhaskell.org/read/mo...

Ну неправда же. Всё там будет хорошо и второй аргумент не будет вычисляться.

#tiegeh

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