[Haskell-cafe] Coercible between data A a b = A a b and (a, b)

[Oleg Grenrus]

Two data types are `Coercible` (as in Data.Coerce) if their representation in memory is the same: they are representiationally equivalent You ask for looser structural isomorphism, consider e.g. 

    data B b = B {-# UNPACK #-} !Int b

and

    (Int, b)

The values of these types have quite different representation/memory layout.

- Oleg

> On 25 Feb 2019, at 16.38, Georgi Lyubenov <godzbanebane at gmail.com> wrote:
> 
> Greetings!
> 
> Is there any reason behind/what is the reason behind
> ```
> data A a b = A a b
> ```
> and
> ```
> (a, b)
> ```
> 
> not being coercible?
> 
> And in general all n-ary constructors not being coercible to one another?
> 
> Thanks in advance!
> 
> =======
> Georgi
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