[Haskell-cafe] what does @ mean?.....

Chaddaï Fouché chaddai.fouche at gmail.com
Fri Dec 28 06:24:51 EST 2007

2007/12/28, Alfonso Acosta <alfonso.acosta at gmail.com>:
> @ works as an aliasing primitive for the arguments of a function
> f x@(Just y) = ...
> using "x" in the body of f is equivalent to use "Just y". Perhaps in
> this case is not really useful, but in some other cases it saves the
> effort and space of retyping really long expressions. And what is even
> more important, in case an error is made when choosing the pattern,
> you only have to correct it in one place.

And in plenty of case it will greatly boost your speed because you
won't be reconstructing the objects against which you matched every
time you want to return them unchanged.


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