GADTs in the wild
gale at sefer.org
Wed Aug 15 23:13:39 CEST 2012
Simon Peyton-Jones wrote:
> This message is to invite you to send me your favourite example of using a
> GADT to get the job done. Ideally I’d like to use examples that are (a)
> realistic, drawn from practice (b) compelling and (c) easy to present
> without a lot of background.
Last year I presented the following simple puzzle to the
That puzzle actually came up in a real-life software project
in Haskell that I was working on.
Several solutions were submitted that used various
Haskell extensions such as rank N types and generics,
as well as a rather cumbersome Haskell 98 solution.
But in my opinion, by far the best solution, using only
GADTs, was submitted by Eric Mertens:
Eric's solution could now be simplified even further
using data kinds.
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