[Haskell-cafe] Merging the OpenGLRaw and gl packages

[Oliver Charles]

On Wed, Sep 30, 2015 at 6:38 PM Sven Panne <svenpanne at gmail.com> wrote:

> IMHO using pattern synonyms vs. plain old Haskell values is to a large
> part just bikeshedding, at least in the trivial case at hand where we talk
> about simple integral values. It basically boils down to the question: Is
>
>    foo x = case x of
>      GL_BAR -> expr1
>      GL_BAZ -> expr2
>      _ -> expr3
>
> really so much better than
>
>    foo x
>      | x == GL_BAR = expr1
>      | x == GL_BAZ = expr2
>      | otherwise = expr3
>

Yes, because the first approach is an expression that you can use anywhere.
Sure, there's little difference when you do it at the "top" of a function
definition, as you're doing. However, it's a lot more significant if you
want to do something like:

foo x = doSomething (case x of ...)

Without pattern synonyms, you either have

foo x = doSomething x'
  where x' | x == ... = ...

or

{-# LANGUAGE MultiWayIf #-}

foo x = doSomething (if | x == ... -> ...)
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