[Haskell-cafe] One-element tuple

[Daniel F]

Can you please elaborate why this inconsistency is annoying and what's the
use of OneTuple?
Genuine question,
thanks.


On Fri, Aug 16, 2013 at 5:35 AM, AntC <anthony_clayden at clear.net.nz> wrote:

> There's an annoying inconsistency:
>
>     (CustId 47, CustName "Fred", Gender Male)  -- threeple
>     (CustId 47, CustName "Fred)                -- twople
> --  (CustId 47)                                -- oneple not!
>     ()                                         -- nople
>
> (That is, it's annoying if you're trying to make typeclass instances for
> extensible/contractable tuples. Yes, I know I could use HLists.)
>
> I'm not happy with either approach I've tried:
>
>     data Oneple a = Oneple a                   -- (or newtype)
>     (Oneple $ CustId 47)                       -- too verbose
>
>     type Oneple a = [a]
>     [CustId 47]                  -- at least looks bracket-y
>
> What do you do?
>
> AntC
>
>
>
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-- 
Sincerely yours,
-- Daniil
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