How functional programming change my Java code
Our story of Java
We start learn Java
or other OO language
DRY & KISS
YAGNI
SOLID & Design Patters
Design Patters
because we use weak language!
We start first job
TDD
BDD
DDD
All those rules we can name
Object Oriented BSDM
First time with
Functional Programming
Functional Programming
===
we have functions
Map, filter, flatMap, reduce
Side effects
Monads
Monoids
Comonads
Category Theory
Whole those Functional Programming Kamasutra
We need to join it somehow...
What happens if you join OO BSDM & FP Kamasutra in one language?
JS
Maybe we need other way?
NO!
Solution?
Trampoline pattern
Wait for Project Amber
Still something wrong...
Do not write
purely functional solution
in non functional language
Apply idea of
functional programming
Immutability
Side effects separation
Context separation
In practise
Business analytic goes functional
Focus on verbs
Identification of common parts
Generalization of nouns
Identification of common actors
Adjectives
Implementation detail
Code is shorter
S(rp)OLID etc.
What != How
Testing
Problems?
Performance
Harder to introduce
Sometimes more code
We need to understand business
Props?
Multithreading goes easy
Refactorization goes easy
We have space for experiments
We deliver value faster
Ecology
We reduce size of spec from ~1000 pages to
~150 pages