Add new generic function: hinitialize

[m-bock]

I found it often useful to have an easy way to generically initialize e.g. a record:

data FillRec = FillRec

instance Initialization FillRec Int where
  initialization _ = 1

instance Initialization FillRec Char where
  initialization _ = 'a'

myRec :: { foo :: Int, bar :: Int, baz :: Char }
myRec = hinitialize FillRec

> myRec                     
{ bar: 1, baz: 'a', foo: 1 }

What do you think? Would it make sense to add this to the library? I have a branch in my fork that implements Initialization and InitializationWithIndex for records.

Alternative names would be: Replicate, Init, Fill....

[natefaubion]

In general, I don't want this library to be a bag of utilities, but just the core abstractions. Not that utilities shouldn't exist, but I don't really want to be the one to maintain them. For example, https://pursuit.purescript.org/packages/purescript-record-studio/1.0.4 is one such utility library.

The line of "core abstraction" is somewhat blurry. We can probably turn anything into some HClass if we try hard enough. For initialization, I think it's a pretty concrete use case rather than an abstraction. That is, it's an HFoldlWithIndex over a RowList. You could potentially initialize an HList of some kind, and that would probably be an HFoldl over it's type spine. I'd wager that any such initialization would likewise be a fold over a type spine. I'm going to lean a bit on the "no" side, in that there's no reason it couldn't exist, but I'm happy enough with it being an ad-hoc thing for records somewhere.