This is just saying that the type of less is any function that takes two
a's as parameters and returns a Bool result. This appears to be a
formalization of the Ord (ordered) data type, where less would be used to
compare two ordered values and return a Bool result, either True or False.
Just a note that the data declaration above is missing a constructor name.
It should probably be something like:
data Ord a = *Ord* { less :: a -> a -> Bool }
Cheers,
Darren
On Wed, Feb 20, 2013 at 1:18 PM, Emanuel Koczwara wrote: Hi, I'm watching Philip Wadler "Faith, Evolution, and Programming
Languages" (very cool by the way):
http://www.youtube.com/watch?v=8frGknO8rIg At 00:24:14 there is strange thing on the slide: data Ord a = { less :: a -> a -> Bool } It's first time I see function type (and where is definition?) in record
syntax. Can somebody explain this? Emanuel _______________________________________________
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