On Tue, Sep 24, 2013 at 6:54 PM, Lyndon Maydwell <maydwell@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@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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