Functional Programming principles

Functional programming has 2 principles:

• Functions are first class values
• pass them as parameter
• return them from a function
• store them in variable
• define function inside a function
• have function literals in the code - like int lieral 42 => anon function
• Operations should map input values to output
• Not change data in place - like what OO does
• Makes data immutable
• No side-effects => referentially transparent