Functional Programming explained to my grandma


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Higher Order Function

In functional programming, a function is defined as a "first order citizen". This means it includes all the properties generally available to any other element, such as the possibility of being affected to a name, returned as a result or passed as a parameter.

A higher-order function is a function that accepts other functions as parameters and/or use a function as the return value.
Let's try it out! Implement the greeting function to return "Hello, [name]" if the name is defined. Otherwise, return "who are you?".

More detailed informations

[Check the scaladoc!] (

How to pass a function as a parameter?

def apply(f: Int => String, v: Int) = f(v)

What make high order functions awesome is this ability to pass a function in parameter.

Let's try to implement the following example: we want to use different sorts. Let's try to use the already-implemented sort function to define the other ones.

_ Language tips _ For this example you can use the wildcard character _ which can match any parameter. It's useful to compare elements to each other.

Implement the differents sort

You can use functions of the collection API the same way you use map and reduce.

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