====== Exam example 1 ======

1. (2p) Write a function in Haskell which returns the **last** element of a list.

2. (2p) Write a function which removes those strings from a list, which are not in the date format. A correct date format is considered: ''DD.MM.YYYY'' where D,M,Y can be any digit.

3. (2p) Implement an Algebraic Datatype which encodes DNA bases: ('A', 'C', 'G', 'T'). Write a function which checks if two DNA sequences are **complementary**. 'A' is complementary to 'T' and 'C' to 'G'. For instance, ''AGTC'' is complementary to ''TCAG''.

4. (1p) Write a function which takes an image (as encoded in the homework), a value k, and creates a ''k x k'' tiling of the image.
Example:
<code haskell>
      .*.
img = **.
      ...
              .*..*..*.
              **.**.**.
              ......... 
              .*..*..*.
tile 3 img =  **.**.**.
              .........
              .*..*..*.
              **.**.**.
              .........

</code>