Frank Poettgen <frank.poett...@post.rxwytxh-ayazcyhzeyn.de>

Assume that the evaluation of a function 'expensive' takes a lot of
time. Hence I want to avoid unnecessary evaluations of 'expensive'.

expensive :: Int -> (Int,Int)
expensive     x  =  (x,x)

f :: Int -> Int
f     x  = fst (expensive x) + snd (expensive x)

Will 'expensive x' be evaluated twice to compute 'f x'?
If so, how can I avoid it?