OlegEfrem/queue-shapeless-excercise

just a play with some existing default implementations

Scotiabank Scala Interview Questions

(c) Scotiabank 2017

A selection of interview problems for developer candidates.

There are 2 exercises to complete.

• Exercise #1 is a data structure question in src/main/scala/test/queue.scala
• Exercise #2 is a question on automatic typeclass derivation using shapeless in src/main/scala/test/eq.scala

You should complete both questions.

Implementation considerations

• Exercise #1 Immutable FIFO Queue borrows from the default scala immutable Queue implementation described here
• Exercise #2 Type Class Derivation with shapeless borrows from Miles Sabin (shapeless creator) on here

• Both solutions are thoroughly tested:
  • scoverage report result is:

      [info] Statement coverage.: 100.00%
      [info] Branch coverage....: 100.00%
      [info] Coverage reports completed
      [info] 100% Coverage !
    

  • FifoQueue is tested here, with the test output:

    [info] FifoQueueTest:
    [info] Time complexity tests
    [info] - isEmpty should have Q(1) in milliseconds
    [info] - insert should have Q(1) in milliseconds
    [info] - remove should have amortized Q(1) = less than 2 milliseconds
    [info] - insert should not be constant in nanoseconds
    [info] Functional tests
    [info]   isEmpty should
    [info]   - return true for empty Queue
    [info]   - return false for non empty Queue
    [info]   insert should
    [info]   - return a new queue with the element prepended
    [info]   - not mutate the original queue
    [info]   remove should
    [info]   - return a new queue with the first inserted element removed
    [info]   - return removed element
    [info]   - not mutate the original queue
    [info]   toString should
    [info]   - return all values for a non empty queue
    [info]   - return empty string for an empty queue
    

  • Type class derivation is tested here, with the test output:

    [info] EqTest:
    [info] Equivalence test
    [info]   product should
    [info]   - be equal to itself
    [info]   - be equal to another instance with same type and values
    [info]   - be different by values
    [info]   coproduct should
    [info]   - be equal to itself
    [info]   - be equal to another instance with same type and values
    [info]   - be different by values
    [info]   custom type should
    [info]   - be equal to itself
    [info]   - be equal to another instance with same type and values
    [info]   - be different by values
    [info]   - be different by types
    

• Code is auto formatted using scalariform;
• Coding style is enforced with scalastyle and wartremover;