On Sat, 11 Sep 2010, Stephen Tetley wrote:
On 11 September 2010 18:21, Jonathan Geddes <geddes.jonat...@gmail.com> wrote:
someUpdate :: MyRecord -> MyRecord
someUpdate myRecord = myRecord
{ field1 = f $ field1 myRecord
, field2 = g $ field2 myRecord
, field3 = h $ filed3 myRecord
}
Applicatively, using no additional libraries, is how I do it:
updateAllThree :: MyRecord -> MyRecord
updateAllThree = (\s a b c -> s { field1 = f a, field2 = g b, field3 = h c})
<*> field1 <*> field2 <*> field3
Cute!
Note - (<$>) is not used, and the left hand function has one extra
argument. This style exploits the fact that (<*>) is the Startling (S)
combinator.
It uses the Applicative instance for functions.
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