contracts.sample.coffee

# in and out
average :: ({name: Str, age: Num}, [...Num]) -> Str
average = (person, loc) ->
    sum = loc.reduce (s1, s2) -> s1 + s2
    "#{person.name} wrote on average 
     #{sum / loc.length} lines of code."

# using your own functions to enforce (just need to handle true or false)
Even = (x) -> x % 2 is 0
Odd = (x) -> x % 2 isnt 0

addEvens :: (!Even) -> !Odd
addEvens = (x) -> x + 1