[Haskell-beginners] How to understand the type "ShowS"?

[yi lu]

I have found the link of difference list. Maybe this helps.

http://www.haskell.org/haskellwiki/Difference_list


On Tue, Sep 24, 2013 at 7:54 PM, yi lu <zhiwudazhanjiangshi at gmail.com>wrote:

>
>
>
> On Tue, Sep 24, 2013 at 7:47 PM, Shrivats <shrvtsnvs at gmail.com> 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" <zhiwudazhanjiangshi at gmail.com> wrote:
>>
>>>
>>> On Tue, Sep 24, 2013 at 6:54 PM, Lyndon Maydwell <maydwell at gmail.com>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] λ :i ShowS
>>>> > type ShowS = String -> String -- Defined in `GHC.Show'
>>>> > [Prelude] λ :i shows
>>>> > shows :: Show a => a -> ShowS -- Defined in `GHC.Show'
>>>> > [Prelude] λ 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 <zhiwudazhanjiangshi at gmail.com>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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