Offer opaque ways to use equality

[treeowl]

As far as I can tell, the library doesn't currently offer fully general ways to eliminate equality without leaning on GHC's fancy equality constraint propagation. The bare-bones basic function is

-- | Eliminate equality evidence
useEq :: a :~: b -> f a -> f b
useEq Refl x = x

[treeowl]

I've edited the description above because I realized one piece was silly.

[glaebhoerl]

This library has been essentially superseded by the Data.Type.Equality module in base, so maybe that would be a better place to add this?

For the record, what's the use case?

[treeowl]

Completeness, mostly. But someone could choose to restrict themselves,
avoiding gcastWith, and therefore limit their language extension support
needs to Rank2Types.

On Nov 11, 2016 5:34 AM, "Gábor Lehel" notifications@github.com wrote:

This library has been essentially superseded by the Data.Type.Equality
https://hackage.haskell.org/package/base-4.9.0.0/docs/Data-Type-Equality.html
module in base, so maybe that would be a better place to add this?

For the record, what's the use case?

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[glaebhoerl]

I don't maintain this any more in any case, but I'd be happy to give you commit access if you want it.