Here's a simple exercise from Stephanie Weirich's class [1] that I am having a hard time with. consider doTwice :: (a -> a) -> a -> a doTwice f x = f (f x) what does this do? ex1 :: (a -> a) -> a -> a ex1 = doTwice doTwice At least, it is clear that there is a parameter to doTwice missing. So, I wanted to do: ex1 y = (doTwice doTwice) y but this gets me nowhere as I don't know how to apply the definition of doTwice inside the parenthesis without naming the arguments. What is the systematic way to evaluate these expressions? I actually got really stumped when I considered. ex2 :: (a -> a) -> a -> a ex2 = doTwice doTwice doTwice doTwice I assume this is not the same as ex2 = (doTwice doTwice doTwice) doTwice what's being applied to what here!? Are there any resources with many practice exercises like this one? Thanks, Dimitri [1] http://www.seas.upenn.edu/~cis552/lectures/Lec2.html