Multi-parameter classes with functional dependencies
When I first learned functional dependencies I remember I was really confused by their syntax. First, it is hard to find it defined: The GHC docs have barely three lines http://www.haskell.org/ghc/docs/latest/html/users_guide/type-extensions.html... and they refer to Mark Jones' paper which has a different notation than GHC's In Mark Jones' paper, the syntax is "tuple" notation, GHC uses | a b c -> d e where concatenation stands for grouping. where one would expect 'a b c' to mean application in Haskell (at the values level and at the type level). So when I first saw this, I thought this must be a kind error (if a has kind *) Otherwise in Haskell, we use parentheses and commas for grouping (export lists, type constraints, deriving) which is somehow wrong because the group in this case is a set, not a tuple. (With that respect, braces in records and let and where are OK, since order is irrelevant, but in do { .. } they are not, but that's how we show our sympathy to C and Java, right.) -- -- Johannes Waldmann -- Tel/Fax (0341) 3076 6479/80 -- ---- http://www.imn.htwk-leipzig.de/~waldmann/ -------