[Haskell-cafe] Fun with Num instances of functions

Henning Thielemann lemming at henning-thielemann.de
Wed Nov 8 06:19:59 EST 2006

Some people have argued, that Num instances of (->) would be nice in order
to add functions nicely, say for
  f, g :: Num a => b -> a
   you would define
  (f+g) x = f x + g x

With an according definition of fromInteger
  fromInteger = const
    numeric literals would also denote constant functions. This allows
  f+2  ==  \x -> f x + 2 .

Even nicer, the mathematically established notation of omitting the
multiplication dot
  2(x+y) :: Integer
 will now be parsed by a Haskell compiler to the most obvious meaning
  2 :: Integer


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