Suppose we want to define a way to represent pairs (or 2-tuples)
in the lambda calculus. We can do this by defining the following
function pair, which takes two arguments and generates a
representation of a pair of those two values.
Give a lambda expression for the function first that takes a pair represented as above and extracts the first item of the pair. Using your definition, I should be able to write first (pair 2 3) and get 2.