Beginner's guide for Functional Programming


This article share basic idea of functional programming for beiginner.

😀 Philosophy

  • Design policy to minimize ‘side effects’
  • Thinking of functional programming is “To add some processing to data” like mathmatic function.
  • It is important not to handle state.

😸 Function

Function is a mechanism that “converts” from input to output.

function: input =(converter)=> output

🗽 Side effects

  • It is changing some data except input one.
  • It is not good to return different output when calling same function with same argument.

🍣 Step for converting functional programming

  • Devide data and behavior. Decompose behavior into some functions without side effects
  • Determine input / output of function so as not to depend on outside condition
  • Use recursion and iteration methods like map, reduce to eliminate side effects

🐹 Object-oriented programming vs Functional programming

Object-oriented programming

Functional programming

🤔 Merits

  • A cause and a result is easy to understand.
  • It is easy to write unit test.

🎃 Demerits

  • As a function type trick, it manipulates data indirectly by passing it to Runtime

🏈 References

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