Chapter 4 Discussion III

All of these problems are stolen from CodingBat. Write function signatures as well as the actual function.

Make sure to write a list of test cases so you have thought through what every part of the problem description means before you start coding.

Some test cases as a haskell file or as a web page

1. (makeLast): Given a list of Int, return a new list twice the length of the original. The last element of the result is the same as the last element of the original list, and all other elements are 0.

2. (swapEnds) Given a list, return a new list with the first and last elements exchanged.

3. (unluckyOne) Say that a 1 immediately followed by a 3 in a list is an “unlucky” 1. Return true if the given list contains an unlucky 1 in the first 2 or last 2 positions in the list.

4. withoutDoubles:: Int -> Int -> Bool -> Int. The first two inputs represent rolls of six-sided dice ([1..6]). Return the sum of the inputs. If the boolean is true, if the dice show the same value, increment one die to the next value, wrapping around to a 1 if the value was a six.

   Examples:

    withoutDoubles 2 3 True == 5
    withoutDoubles 3 3 True == 7
    withoutDoubles 3 3 False == 6
   

5. (teenSum) Given 2 ints, return their sum. However, “teen” values in the range 13..19 inclusive, are extra lucky. So if either value is a teen, just return 19.

6. (teaParty) We are having a party with amounts of tea and candy. Return the int outcome of the party encoded as 0=bad, 1=good, or 2=great. A party is good (1) if both tea and candy are at least 5. However, if either tea or candy is at least double the amount of the other one, the party is great (2). However, in all cases, if either tea or candy is less than 5, the party is always bad (0).

7. (xyBalance) We’ll say that a String is xy-balanced if for all the ‘x’ chars in the string, there exists a ‘y’ char somewhere later in the string. So “xxy” is balanced, but “xyx” is not. One ‘y’ can balance multiple ‘x’s. Return true if the given string is xy-balanced. Examples:

     xyBalance "pixxa" == False
     xyBalance "pixely art" == True
     xyBalance "xay anythxng" == False
   

8. (unluckyOne2) Continuing the unluckyOne problem, return true if a list contains an unlucky 1 in any position.