Solution for the first question.
Solution for the second exercise.
Solution for the third exercise.
Solution for the fourth exercise.
Solution for the fifth exercise.
Solution for the sixth exercise.
Improving the boolean check.
Removing optional parenthesis.
Fix missing pattern matching and reorder the existing one.
Use _ for unused argument.
Use the null pattern matching.
Changing the pattern matching to return the last argument.
Merge pull request #4 from laurocaetano/ch-04

Ch 04