This file is now a LaTeX file with embedded Haskell:
\begin{code}
module Jan12b where
— let’s play with lists a little
— recall
— data [] a = [] | a : [a]
map’ :: (a -> b) -> [a] -> [b]
map’ f [] = []
map’ f (x : xs) = f x : map’ f xs
filter’ :: (a -> Bool) -> [a] -> [a]
filter’ p [] = []
filter’ p (x : xs) | p x = x : filter’ p xs
| otherwise = filter’ p xs
isEven :: Integer -> Bool
isEven x = x `mod` 2 == 0
— Things we tried:
— 7 `mod` 2
— filter’ isEven [(-15)..15]
— list comprehension:
— [ x | x <- l, isEven x]
-- rather list 'set' comprehension in math -- { x \in l | isEven x }
l :: [Integer]
l = [-15..15]
--
-- if we want to print something, like this:
main :: IO ()
main = print "Hello World!"
\end{code}