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Num instance for functions

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(merely a copy of my mail to Haskell-Cafe)
 
(more Humor than Proposal)
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[[Category:Humor]]
 
[[Category:Proposals]]
 
[[Category:Proposals]]

Revision as of 13:08, 17 April 2007

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
! :-)


See also