Difference between revisions of "Num instance for functions"
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(more Humor than Proposal) |
(Formatting) |
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| Line 2: | Line 2: | ||
to add functions nicely, say for |
to add functions nicely, say for |
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<haskell>f, g :: Num a => b -> a</haskell> |
<haskell>f, g :: Num a => b -> a</haskell> |
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| − | + | you would define |
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<haskell>(f+g) x = f x + g x</haskell> |
<haskell>(f+g) x = f x + g x</haskell> |
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With an according definition of <hask>fromInteger</hask> |
With an according definition of <hask>fromInteger</hask> |
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<haskell>fromInteger = const</haskell> |
<haskell>fromInteger = const</haskell> |
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| − | + | numeric literals would also denote constant functions. This allows |
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<haskell>f+2 == \x -> f x + 2</haskell>. |
<haskell>f+2 == \x -> f x + 2</haskell>. |
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| Line 13: | Line 13: | ||
multiplication dot |
multiplication dot |
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<haskell>2(x+y) :: Integer</haskell> |
<haskell>2(x+y) :: Integer</haskell> |
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| − | + | will now be parsed by a Haskell compiler to the most obvious meaning |
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<haskell>2 :: Integer</haskell> |
<haskell>2 :: Integer</haskell> |
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| − | + | ! :-) |
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Revision as of 13:10, 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
! :-)