[Haskell-beginners] list range

[Mike Meyer]

On Wed, 28 Dec 2011 19:08:08 +0000
Henry Lockyer <henry.lockyer at ntlworld.com> wrote:

> On 28 Dec 2011, at 19:05, Henry Lockyer wrote:
> Sorry, should have read your question a second time instead of posting a quick reply ;-)
> I think it is syntactic sugar..

Others say it's syntactic sugar, but your advice:

> > If you have GHCI installed, then I recommend using the ":t" command to explore the types of Haskell expressions.

is still good, *and* can answer that question:

> >> Is list range (for example: [1..10]) a language construct or a function?
> >> What type does it have?

If it's a function, then :t will know about it, even in that odd
form if you wrap it in parens. For instance:

*Main> :t (+)
(+) :: Num a => a -> a -> a

even if it's a constructor, like:

*Main> :t ((,))
((,)) :: a -> b -> (a, b)

But trying the [..] notation, you get:

*Main Network.HTTP> :t ([..])

<interactive>:1:3: parse error on input `..'

I.e. - it's syntactic sugar to generate a value. If it were a
function, the type would be something like:

([..]) :: Enum a => a -> a -> [a]

       <mike
-- 
Mike Meyer <mwm at mired.org>		http://www.mired.org/
Independent Software developer/SCM consultant, email for more information.

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