[Haskell-cafe] Need feedback on my Haskell code

CK Kashyap ck_kashyap at yahoo.com
Fri Jul 31 08:12:32 EDT 2009


I personally find 
map maySwitch (unfoldr go (x1,y1,0)) and map maySwitch $ unfoldr go (x1,y1,0) more intuitive.

I can read it as map the maySwitch function over the list generated from the unfolding.

Is there any difference in the evaluation steps between the composition version and the non-composition version?

Regards,
Kashyap




________________________________
From: david48 <dav.vire+haskell at gmail.com>
To: Ryan Ingram <ryani.spam at gmail.com>
Cc: Johan Tibell <johan.tibell at gmail.com>; haskell-cafe at haskell.org; CK Kashyap <ck_kashyap at yahoo.com>
Sent: Friday, July 31, 2009 11:56:17 AM
Subject: Re: [Haskell-cafe] Need feedback on my Haskell code

On Fri, Jul 31, 2009 at 5:53 AM, Ryan Ingram<ryani.spam at gmail.com> wrote:

> Read ($) as a parenthesis that extends as far to the right as
> possible; so you can write, for example:

That doesn't always work, for example :

map (+2) . map (*1) $ [1,2,3]
= [4,6,8]

Now replacing the $ by a parenthesis that extends as far to the right
as possible :

map (+2) . map (*1) ( [1,2,3] )

<interactive>:1:11:
    Couldn't match expected type `a -> [a1]'
           against inferred type `[a2]'
    In the second argument of `(.)', namely `map (* 2) ([1, 2, 3])'
    In the expression: map (+ 2) . map (* 2) ([1, 2, 3])
    In the definition of `it': it = map (+ 2) . map (* 2) ([1, 2, 3])



      
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