[Haskell-cafe] Where does ~> come from?

Wolfgang Jeltsch g9ks157k at acme.softbase.org
Tue Feb 19 16:15:57 EST 2008

Am Dienstag, 19. Februar 2008 18:26 schrieben Sie:
> […]

> However, I was told this:  ~> a b is a ~> b, but if I write c a b and
> wish the effect of a `c` b. This would not work. ~> as an infix operator
> has a special place in GHC. It is not "just a type variable".

Sorry, but I don’t understand fully what you mean. :-(  But nevertheless,
a ~> b is not the same as ~> a b but as (~>) a b.  It’s just like with 
ordinary operators where a + b is the same as (+) a b.

~> is not special in GHC.  You could use, for example, ### instead of ~> and 
get the same results.  However, GHC accepts type operators only if you tell 
it to do so.  Give GHC the option -XTypeOperators or insert

    {-# LANGUAGE TypeOperators #-}

at the beginning of your source file.

> […]

Best wishes,

More information about the Haskell-Cafe mailing list