# Papers, please !

## Generalization of Named

I introduced the `Named`

data in my last article, and I tried to generalize a bit.

I came to the `Civility`

idea and more, the `Citizen`

data. They are some information that define an object in a context, but does not define entirely it (like a `Name`

: it identify yourself as a citizen, but not has a Human being). So a `Citizen`

is something with its papers:

But that is likely a tuple, and in fact, all the previous instances are correctly defined for Tuples!

So *in-fine* we have

## More results than the ones on the previous-Named ?

### Monads and CoMonads together ?

Some pretty results are coming if the papers are an instance of a `Monoid`

: We have `Applicative`

and `Monad`

instances:

Theses samples of code are taken from [http://hackage.haskell.org/package/base-4.11.0.0/docs/src/GHC.Base.html#line-433]

Basically, if there are empty papers and a way to concatenate them, `Citizen`

become a `Monad`

.

### BiFunctor

Yes, you apply a function independently on papers and on the object, so you are also wining a `BiFunctor`

instance

## Utility: the Grouped example

`Grouped`

is a common data:

You can find it in the `Weigh`

package. It represents a kind of *Rose Tree*.

You can write a pretty function that transform the structure in a “after-parsing” one:

Now imagine you have a `tree :: Grouped (Named File)`

representing a file tree in a Unix system

Then you have:

For example:

```
>>> printTree $ Group "" [Simple (withName "info.txt" ()), Group "bin" [Simple (withName "ghc" ()),Simple (withName "stack" ())]]
/info.txt
/bin/ghc
/bin/stack
```