Deforestation2

import Data.Char
import Data.List

func = map toUpper . filter (/= 'a')

func' xs = map toUpper $ filter (/= 'a') xs

func'' xs = case filter (/= 'a') xs of
                                    [] -> []
                                    x:xs -> toUpper x : map toUpper xs

func''' xs = case (case xs of
                           [] -> []
                           x:xs -> case x /= 'a' of
                                                 True -> x : filter (/= 'a') xs
                                                 False -> filter (/= 'a') xs) of
                                                                              [] -> []
                                                                              x:xs -> toUpper x : map toUpper xs

func'''' xs = case xs of
                      [] -> case [] of
                                    [] -> []
                                    x:xs -> toUpper x : map toUpper xs
                      x:xs -> case (case x /= 'a' of True -> x : filter (/= 'a') xs
                                                     False -> filter (/= 'a') xs) of
                                                                                  [] -> []
                                                                                  x:xs -> toUpper x : map toUpper xs

func''''' xs = case xs of
                       [] -> []
                       x:xs -> case x /= 'a' of
                                             True -> case x : filter (/= 'a') xs of
                                                                                 [] -> []
                                                                                 x:xs -> toUpper x : map toUpper xs
                                             False -> case filter (/= 'a') xs of
                                                                              [] -> []
                                                                              x:xs -> toUpper x : map toUpper xs

func'''''' xs = case xs of
                        [] -> []
                        x:xs -> case x /= 'a' of
                                              True -> toUpper x : map toUpper (filter (/= 'a') xs)
                                              False -> case filter (/= 'a') xs of
                                                                               [] -> []
                                                                               x:xs -> toUpper x : map toUpper xs

answer xs = case xs of [] -> []
                       x:xs -> case x /= 'a' of
                                             True -> toUpper x : answer xs
                                             False -> answer xs