# [racket] missing solution 20.2.2 ex:fancy-contracts

A candidate for a solution.
Exercise 20.2.2. Formulate contracts for the following functions:
1. sort, which consumes a list of numbers and a function that consumes
two numbers (from the list) and produces a boolean; sort produces a
list of numbers.
2. map, which consumes a function from numbers to numbers and a list
of numbers; it also produces a list of numbers.
3. project, which consumes a list of lists of symbols and a function
from lists of symbols to symbols; it produces a list of symbols.
Solution.
sort: (listof number) (number number -> boolean) -> (listof number)
map: (number -> number) (listof number) -> (listof number)
project: (listof (listof symbol)) ((listof symbol) -> symbol) -> (listof symbol)