-- Informatics 2A Assignment 1, Nov 2016
-- MH test program 3

-- Representing infinite lists of booleans as functions

head :: (Integer -> Bool) -> Bool ;
head l = l 0;

tail :: (Integer -> Bool) -> (Integer -> Bool) ;
tail l n = l(n+1) ;

cons :: Bool -> (Integer -> Bool) -> Integer -> Bool ;
cons n l m = if m == 0 then n else l(m - 1) ;

inTeens :: Integer -> Bool ;
inTeens n = if 13 <= n then n <= 19 else False ;

-- Test expression: (if (cons False inTeens) 13 then 2 else 0) + (if (head (tail inTeens)) then 0 else 1)
-- Type should be:  Integer
-- Value should be: 1