Source of exercises
    http://exercism.io



https://medium.com/@markcanlasnyc/scala-saturday-functions-for-the-object-oriented-4218f9ed192b#.dw8x8zxvb

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Map-Reduce in Scala

https://madusudanan.com/blog/scala-tutorials-part-9-intro-to-functional-programming/


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bash scripting

https://likegeeks.com/bash-script-easy-guide/
https://likegeeks.com/linux-bash-scripting-awesome-guide-part3/


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collatz
http://codepen.io/benlorantfy/pen/KWzXoX