Usage of ! in a Haskell type [duplicate]

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Possible Duplicate:

What does the exclamation开发者_高级运维 mark mean in a Haskell declaration?

In Alex the generated boilerplate code includes

data AlexPosn = AlexPn !Int  -- absolute character offset
                       !Int  -- line number
                       !Int  -- column number

What does the ! in front of the Int indicate?

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It´s a strictness flag as oposed to lazy evaluation.