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Re: [Haskell-cafe] What's going on here?

Subject: Re: [Haskell-cafe] What's going on here?
From: michael rice
Date: Sat, 16 Jan 2010 19:16:15 -0800 PST
Dumb! I've been Lisp and just slipped over to Haskell to check on something.

Thanks,

Michael

--- On Sat, 1/16/10, VoidPrayer <[email protected]> wrote:

From: VoidPrayer <[email protected]>
Subject: Re: [Haskell-cafe] What's going on here?
To: [email protected]
Date: Saturday, January 16, 2010, 10:05 PM

å 2010å 1æ 17æ æææ 11:02:59ïmichael rice åé:
> I don't see anything wrong with this function, which just subtracts 1 from
>  the first element of an Int list (if there is a first element).
>
> Michael
>
> My function:
>
> dropFirst :: [Int] -> [Int]
> dropFirst [] = []
> dropFirst (x:xs) = (x-1) : xs
>
> My output:
> > :l dropfirst
>
> [1 of 1] Compiling Main             ( dropfirst.hs, interpreted )
> Ok, modules loaded: Main.
> *Main> dropFirst [3 4 5 6]

Use dropFirst [3,4,5,6], I think.

>
> <interactive>:1:11:
>     No instance for (Num (t -> t1 -> t2 -> Int))
>       arising from the literal `3' at <interactive>:1:11-17
>     Possible fix:
>       add an instance declaration for (Num (t -> t1 -> t2 -> Int))
>     In the _expression_: 3 4 5 6
>     In the first argument of `dropFirst', namely `[3 4 5 6]'
>     In the _expression_: dropFirst [3 4 5 6]
> *Main>
>
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