Re: [Haskell-cafe] Spot the difference!

test1 n _ = 1 + n test2 n = \_ -> 1 + n

I don't know if it's still the case, but GHC used to compile different code for these at high optimisation levels. The first was essentially compiled to:

test1 = \n _ -> 1+n

And the second to:

test2 = \n -> let x = n+1 in \_ -> x

The difference is that test1 is faster if it's usually fully applied, test2 is fully lazy.

Fully lazy? Can you elaborate please? Thanks, Paul