urbmic/scalania

Exercises for Scala get-togethers

Scalania - exercises to learn Scala

There's an idea to host regular Scala hack-a-thons in Warsaw, Poland and the project is to let people get started code-wise.

This is a sbt-based project with tests that are supposed to help people learn (and ultimately master) Scala while solving problems as described in S-99: Ninety-Nine Scala Problems and do the exercises that accompany a Scala course Scala i programowanie funkcyjne.

The website of the meetings is http://scalania.pl.

How to get started with the project

• Download the latest version of sbt.

• Run sbt ~exercises/test

    $ sbt ~exercises/test
    [info] Loading global plugins from /Users/jacek/.sbt/plugins
    [info] Loading project definition from /Users/jacek/oss/scalania/project
    [info] Set current project to scalania (in build file:/Users/jacek/oss/scalania/)
    [info] Set current project to exercises (in build file:/Users/jacek/oss/scalania/)
    [info] Updating {file:/Users/jacek/oss/scalania/}exercises...
    [info] Resolving org.scala-lang#scala-reflect;2.10.0 ...
    [info] Done updating.
    [info] Compiling 3 Scala sources to /Users/jacek/oss/scalania/exercises/target/scala-2.10/classes...
    [info] Compiling 3 Scala sources to /Users/jacek/oss/scalania/exercises/target/scala-2.10/test-classes...
    [info] P03Spec
    [info] P03 should
    [info] x Find the Kth element of a list
    [error]    an implementation is missing (P03.scala:4)
    [info] Total for specification P03Spec
    [info] Finished in 32 ms
    [info] 1 example, 1 failure, 0 error
    [info] P01Spec
    [info] P01 should
    [info] x Find the last element of a list
    [error]    an implementation is missing (P01.scala:4)
    [info] Total for specification P01Spec
    [info] Finished in 31 ms
    [info] 1 example, 1 failure, 0 error
    [info] P02Spec
    [info] P02 should
    [info] x Find the last but one element of a list
    [error]    an implementation is missing (P02.scala:4)
    [info] Total for specification P02Spec
    [info] Finished in 3 ms
    [info] 1 example, 1 failure, 0 error
    [error] Failed: : Total 3, Failed 3, Errors 0, Passed 0, Skipped 0
    [error] Failed tests:
    [error]         pl.japila.s99.P02Spec
    [error]         pl.japila.s99.P03Spec
    [error]         pl.japila.s99.P01Spec
    [error] (exercises/test:test) sbt.TestsFailedException: Tests unsuccessful
    [error] Total time: 17 s, completed Aug 6, 2013 7:06:24 AM
  

Make the tests pass (make them all green). In the above snippet the problems P01 to P03 fail (an implementation is missing).

• Once all the tests get green (the success shows up as a result of running the tests), you're almost done.

    [info] Compiling 1 Scala source to /Users/jacek/oss/scalania/exercises/target/scala-2.10/classes...
    [info] P03Spec
    [info] P03 should
    [info] + Find the Kth element of a list
    [info] Total for specification P03Spec
    [info] Finished in 25 ms
    [info] 1 example, 0 failure, 0 error
    [info] P01Spec
    [info] P01 should
    [info] + Find the last element of a list
    [info] Total for specification P01Spec
    [info] Finished in 24 ms
    [info] 1 example, 0 failure, 0 error
    [info] P02Spec
    [info] P02 should
    [info] + Find the last but one element of a list
    [info] Total for specification P02Spec
    [info] Finished in 1 ms
    [info] 1 example, 0 failure, 0 error
    [info] Passed: : Total 3, Failed 0, Errors 0, Passed 3, Skipped 0
    [success] Total time: 3 s, completed Aug 6, 2013 8:15:51 PM
  

• "Almost" makes a difference, really. To finish the exercises, run sbt exercises/scalastyle to ensure high quality of your solutions that is manifested with Found 0 errors and Found 0 warnings in the output.

    jacek:~/oss/scalania
    $ sbt exercises/scalastyle
    [info] Loading global plugins from /Users/jacek/.sbt/plugins
    [info] Loading project definition from /Users/jacek/oss/scalania/project
    [info] Set current project to scalania (in build file:/Users/jacek/oss/scalania/)
    [info] Set current project to scalania-exercises (in build file:/Users/jacek/oss/scalania/)
    Processed 3 file(s)
    Found 0 errors
    Found 0 warnings
    Finished in 5 ms
    [success] created: /Users/jacek/oss/scalania/exercises/target/scalastyle-result.xml
    [success] Total time: 1 s, completed Aug 6, 2013 7:30:04 PM
  

How to contribute

A quite productive approach to master Scala is to further extend the project with new tests that show what the language can offer.

Fork the project and send pull requests on GitHub.

Please use topic branches when sending pull requests rather than committing directly to master in order to minimize unnecessary merge commit clutter.

Tools used

• http://www.scala-sbt.org/
• https://github.com/kobmic/plain-scala.g8
• http://aperiodic.net/phil/scala/s-99/