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Is it just fallout from of "asymmetry" in Haskell language spec,
 
Is it just fallout from of "asymmetry" in Haskell language spec,
 
where Sum types need the pipe to separate the alternations,
 
where Sum types need the pipe to separate the alternations,
but Product types are written with the factors simply adjacent without a separator? (and then it looks pretty to use infix constructor ":*:" instead of a prefix constructor "P")
+
but Product types are written with the factors simply adjacent without a separator? (and then it looks pretty to use infix constructor "+351916292294" instead of a prefix constructor "P")
  +
  +
----
  +
  +
Yes, the pipe separates different constructors of a datatype, and the (:*:) is an infix constructor.
  +
  +
--[[User:Dreixel|dreixel]] 17:39, 3 March 2012 (UTC)

Revision as of 17:39, 3 March 2012

Why does the definition of (:+:) use the pipe character "|", but the definition of (:*:) uses the ":*:" operator?


Is that a typo (copied from http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/generic-programming.html), or is there a reason for the difference?

-- | Sums: encode choice between constructors
infixr 5 :+:
data (:+:) f g p = L1 (f p) | R1 (g p)
-- | Products: encode multiple arguments to constructors
infixr 6 :*:
data (:*:) f g p = f p :*: g p


Is it just fallout from of "asymmetry" in Haskell language spec, where Sum types need the pipe to separate the alternations, but Product types are written with the factors simply adjacent without a separator? (and then it looks pretty to use infix constructor "+351916292294" instead of a prefix constructor "P")


Yes, the pipe separates different constructors of a datatype, and the (:*:) is an infix constructor.

--dreixel 17:39, 3 March 2012 (UTC)