[Haskell-cafe] Equality Contstraint?

Brandon Allbery allbery.b at gmail.com
Fri May 15 01:47:35 UTC 2015

On Thu, May 14, 2015 at 9:17 PM, Michael Jones <mike at proclivis.com> wrote:

> I kind of think it is some kind of equality constraint but can’t find
> documentation. Perhaps if I knew what it was called I might succeed in
> finding something. If it is an equality constraint, please provide a
> reference if you have one. I did not find anything in a search including
> GHC, etc.

~ is an equality constraint only in a type constraint (foo :: (x ~ y) =>
...). In a pattern, it indicates the pattern matches lazily instead of the
usual strict match.

brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
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