Haskell Fan Site

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In other words, I used to think functional programming languages were only of theoretical interest because they frowned upon side effects. Haskell is the first widespread language to follow all three laws. In other words, Haskell’s greatest contribution is not that it does away with side effects (such a language is indeed useless), but rather that it constitutionally separates pure and impure functions without encumbering the syntax of either.

Source: www-cs-students.stanford.edu