[Haskell-cafe] Constructor question

[Ivan Lazar Miljenovic]

michael rice <nowgate at yahoo.com> writes:

> From: Data.Complex
>
> data (RealFloat a) => Complex a
>   = !a :+ !a
>
> What's the purpose of the exclamation marks?

Forcing; it means that the values are evaluated (up to WHNF) before the
Complex value is constructed:

http://www.haskell.org/ghc/docs/6.12.1/html/users_guide/bang-patterns.html

-- 
Ivan Lazar Miljenovic
Ivan.Miljenovic at gmail.com
IvanMiljenovic.wordpress.com