Ch 02 Quiz 4

On paper, write the function

f :: [Int] -> [Int]

This function has the following properties:

• Skip input numbers that are below 100.
• Other numbers should be in the output list.
• Except if you hit 999 the process ends immediately, without output.

Examples:

checks1 = [ f [10,500,999,888] == [500] ]

Post-Quiz Study Guide

Memorize these templates.

Copy all of the input numbers to the output.

laze0 :: [Int] -> [Int]
laze0 [] = []
laze0 (x:xs) = x : laze0 xs

Skip odd numbers.

laze1 :: [Int] -> [Int]
laze1 [] = []
laze1 (x:xs)
  | odd x     = laze1 xs
  | otherwise = x : laze1 xs

Stop when you get to 10.

laze2 :: [Int] -> [Int]
laze2 [] = []
laze2 (x:xs)
   | x == 10    = []
   | otherwise  = x : laze2 xs

Alternate version. (Fancy, not the basic memorized template.)

laze2b :: [Int] -> [Int]
laze2b [] = []
laze2b (10:xs) = []
laze2b (x:xs) : laze2b xs