Functional Programming explained to my grandma


Dummy example of lambda

Until now we have used a lot of functions. We specified that we want them to be pure (no side effect). We have seen that we can pass it as a parameter to other functions or use it in a return. Also, we have seen that by currying we can define precise functions that improve readability and reuse.

However, you will run into a function has no reason to be reused. In this case, we want to use it anonymously. This is what we call a lambda expression.

In this example, the operation function takes a function as a parameter and will apply it to each number from 1 to x, where x is the high limit parameter.

Let's try to use it to define three different functions:

  • sum : a function to add each number from 1 to x
  • sumSquare: a function to add each squared number from 1 to x
  • sumPeer: a function to add the x first odd numbers

To complete these, let's use lambdas as the parameter of "operation"

Implement different sums
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