Exercises

02. Starting Out

Using IHaskell: https://github.com/gibiansky/IHaskell

The first function has been completed as an example. All the other functions are undefined. They can be implemented in one line using the material covered in http://learnyouahaskell.com/starting-out

All indices are zero based.

1. Find the penultimate element in list l



In [1]:

    
penultimate l = last (init l)

-- Test:
penultimate [1,4,10,11,22] == 11









    





True

2. Find the element at index k in list l

For example: "findK 2 [0,0,1,0,0,0]" returns 1



In [ ]:

    
findK k l = undefined

-- Test:
findK 2 [0,0,1,0,0,0] == 1

3. Determine if list l is a palindrome



In [ ]:

    
isPalindrome l = undefined

-- Test:
isPalindrome "anna" && not (isPalindrome "anne")

4. Duplicate the elements in list xs

For example "duplicate [1,2,3]" would give the list [1,1,2,2,3,3]

Hint: The "concat [l]" function flattens a list of lists into a single list.

You can see the function definition by typing ":t concat" into the interpreter. Perhaps try this with other variables and functions
For example: concat [[1,2,3],[3,4,5]] returns [1,2,3,3,4,5]



In [ ]:

    
duplicate xs = undefined

-- Test:
duplicate [1,2,3] == [1,1,2,2,3,3]

5. Imitate the functinality of zip

For example "ziplike [1,2,3] ['a', 'b', 'c', 'd']" returns [(1,'a'), (2, 'b'), (3, 'c')]

Hint: the function "min x y" returns the lower of values x and y



In [ ]:

    
ziplike xs ys = undefined

-- Test:
ziplike [1,2,3] ['a', 'b', 'c', 'd'] == [(1,'a'), (2, 'b'), (3, 'c')]

6. Split a list l at element k into a tuple: The first part up to and including k, the second part after k

For example "splitAtIndex 3 [1,1,1,2,2,2]" returns ([1,1,1],[2,2,2])



In [ ]:

    
splitAtIndex k l = undefined

-- Test:
splitAtIndex 3 [1,1,1,2,2,2] == ([1,1,1],[2,2,2])

7. Drop the element at index k in list l

For example "dropK 3 [0,0,0,1,0,0,0]" returns [0,0,0,0,0,0]



In [ ]:

    
dropK k l = undefined

-- Test:
dropK 3 [0,0,0,1,0,0,0] == [0,0,0,0,0,0]

8. Extract elements between ith and kth element in list l. Including i, but not k

For example, "slice 3 6 [0,0,0,1,2,3,0,0,0]" returns [1,2,3]



In [ ]:

    
slice i k l = undefined

-- Test:
slice 3 6 [0,0,0,1,2,3,0,0,0] == [1,2,3]

9. Insert element x in list l at index k

For example, "insertElem 2 5 [0,0,0,0,0,0]" returns [0,0,0,0,0,2,0]



In [ ]:

    
insertElem x k l = undefined

-- Test:
insertElem 2 5 [0,0,0,0,0,0] == [0,0,0,0,0,2,0]

10. Rotate list l n places left

For example, "rotate 2 [1,2,3,4,5]" gives [3,4,5,1,2]



In [ ]:

    
rotate n l = undefined

-- Test
rotate 2 [1,2,3,4,5] == [3,4,5,1,2]