volume :: Fruit FruitType -> Double
volume F{radius=r,len=l,fType=Orange} = (4.0/3.0) * pi * r * r * r

volume F{radius=r,len=l,fType=Apple} = (4.0/3.0) * pi * r * r * r
volume F{radius=r,len=l,fType=Banana} = pi * (r * r) * l
volume F{radius=r,len=l,fType=Watermelon} = (4.0/3.0) * pi * (2.0 * r)
* l * (0.5 * l)

Can anyone explain the above pattern matching syntax? I've never seen it before...

Thanks,

Patrick