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Today's Topics:
1. Re: How to understand the type "ShowS"? (Kim-Ee Yeoh)
2. Re: How to understand the type "ShowS"? (yi lu)
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Message: 1
Date: Tue, 24 Sep 2013 18:50:48 +0700
From: Kim-Ee Yeoh <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] How to understand the type "ShowS"?
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On Tue, Sep 24, 2013 at 6:43 PM, yi lu <[email protected]>wrote:
> I have just looked at the API of Prelude, and I remember similar
> definition for parallel haskell.
How far have you gotten with LYAH? Or Hutton's textbook?
What does a search on "haskell intro type system" reveal?
-- Kim-Ee
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Message: 2
Date: Tue, 24 Sep 2013 19:54:08 +0800
From: yi lu <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] How to understand the type "ShowS"?
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On Tue, Sep 24, 2013 at 7:47 PM, Shrivats <[email protected]> wrote:
> What does `show "asdf"` give you in ghci? What Lyndon showed you was that
> this function is equivalent to `shows x s = show x ++ s`.
>
> Ah, it works a bit like "++" ?
> Have fun,
>
> Shrivats
> On Sep 24, 2013 5:09 PM, "yi lu" <[email protected]> wrote:
>
>>
>> On Tue, Sep 24, 2013 at 6:54 PM, Lyndon Maydwell <[email protected]>wrote:
>>
>>> Looks like it's a convenience for building up a compositions of "Show"s.
>>>
>>> ShowS is indeed a synonym for a function. The type of shows alone isn't
>>> enough to figure out how it behaves exactly, but testing it out in GHCi is
>>> telling:
>>>
>>>
>>> > [Prelude] ? :i ShowS
>>> > type ShowS = String -> String -- Defined in `GHC.Show'
>>> > [Prelude] ? :i shows
>>> > shows :: Show a => a -> ShowS -- Defined in `GHC.Show'
>>> > [Prelude] ? shows "asdf" "qwer"
>>> > "\"asdf\"qwer"
>>>
>>> I don't know the meaning of this result.
>>
>>
>>
>>>
>>> On Tue, Sep 24, 2013 at 8:15 PM, yi lu <[email protected]>wrote:
>>>
>>>> Prelude> :i ShowS
>>>> type ShowS = String -> String -- Defined in `GHC.Show'
>>>>
>>>> It is a type of a function? I cannot understand this type, and don't
>>>> know how to create functions of this type.
>>>>
>>>> And this function "shows"
>>>>
>>>> Prelude> :i shows
>>>> shows :: Show a => a -> ShowS -- Defined in `GHC.Show'
>>>>
>>>> I don't know how this function works.
>>>>
>>>> Yi
>>>>
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