Re[2]: [Haskell-cafe] On to applicative

Hello michael, Tuesday, August 31, 2010, 9:27:17 PM, you wrote: f :: Int -> Int i.e. it's used when you define function types

So it's a type constructor, not a type? Could you please provide a simple example of its usage?

Michael

--- On Tue, 8/31/10, Vo Minh Thu wrote:

From: Vo Minh Thu Subject: Re: [Haskell-cafe] On to applicative To: "michael rice" Cc: haskell-cafe@haskell.org Date: Tuesday, August 31, 2010, 1:17 PM

2010/8/31 michael rice

...

"Learn You a Haskell ..."  says that (->) is a type just like Either. Where can I find its type definition?

You can't define it *in* Haskell as user code. It is a built-in infix type constructor (Either or Maybe are type constructors too, not just types). In fact, if you want to implement a simple, typed functional language, you'll find it is the only built-in type constructor you have to implement (as the implementor of the language).

Also,   Show a => a is a type too, but you won't find a definition for 'a' or for '=>'. All those things are defined by the language.

Cheers, Thu

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