Functional programming and non-functional programming

Question

In my second year of University we were \"taught\" Haskell, I know almost nothing about it and even less about functional programming.

What is functional programming

Answer 1

I find What Is Functional Programming? to be useful

Functional programming is about writing pure functions, about removing hidden inputs and outputs as far as we can, so that as much of our code as possible just describes a relationship between inputs and outputs.

Prefer explicit when param

public Program getProgramAt(TVGuide guide, int channel, Date when) {
  Schedule schedule = guide.getSchedule(channel);

  Program program = schedule.programAt(when);

  return program;
}

over

public Program getCurrentProgram(TVGuide guide, int channel) {
  Schedule schedule = guide.getSchedule(channel);

  Program current = schedule.programAt(new Date());

  return current;
}

A functional language is actively hostile to side-effects. Side-effects are complexity and complexity is bugs and bugs are the devil. A functional language will help you be hostile to side-effects too.