[Haskell-beginners] small question

[Bastian Erdnüß]

On Oct 19, 2010, at 16:13, Mohamed wrote:

> Hello folks,
> 
> just a quickie here and would appreciate any help...
> 
> In this expression:
> 
> 
> 
> instance OBSERVATIONS Drinkability WaterWell Volunteer where
>    observe (Drinkability waterWell) volunteer = volunteer {vReport = 
>       if (odorQuale (perceive (Odor waterWell) volunteer) == True && 
> clarityQuale (perceive (Clarity waterWell) volunteer) == True && fullnessQuale 
> (perceive (Fullness waterWell) volunteer) == True) then (if (honesty) then 
> "drinkable" else "undrinkable") else (if (honesty) then "undrinkable" else 
> "drinkable")}

I suppose this could also be written

  instance OBSERVATIONS Drinkability WaterWell Volunteer where
    observe (Drinkability waterWell) volunteer =
      volunteer { vReport = drinkability } where
        drinkability = undrinkableIf $ honesty volunteer `xor`
          odorQuale     (perceive (Odor     waterWell) volunteer) &&
          clarityQuale  (perceive (Clarity  waterWell) volunteer) &&
          fullnessQuale (perceive (Fullness waterWell) volunteer)
        undrinkableIf True  = "undrinkable"
        undrinkableIf False = "drinkable"

  xor False = id
  xor True  = not
  infixr 2 xor

if I didn't make a mistake.  It's maybe a little bit more readable.

Btw.  How would I rewrite this in applicative style?  I came up with something like

  drinkability = undrinkableIf $ xor . honesty
    <*> ( (&&) . odorQuale     . (perceive $ Odor     waterWell)
    <*>   (&&) . clarityQuale  . (perceive $ Clarity  waterWell)
    <*>          fullnessQuale . (perceive $ Fullness waterWell) ) $ volunteer

(not sure it would still compile).  However, seems not that readable anymore.  Is it not recommended to use applicative style with binary infix operators?  Or is there a way to make them readable again?

Regards,
Bastian