OOP is not Deador why we should stop seeing FP as its opponent or as silver bullet

Hernán A. Wilkinson

@hernanwilkinson

agile software development & services

This will not be a war!

A little bit of Context…

A little bit of History…

Structured Programming, when?

Object Oriented Programming, when?

Simula 67Ole-Johan Dahl y Kristen Nygaard

Simula 67Ole-Johan Dahl y Kristen Nygaard

OOP before Structured Programming??

Functional Programming, when?

John McCarthy

What does make Lisp great?(always great! not, “great again” )

LISP

(define (filtrar lista condicion)

(cond

((esta-vacia? lista) lista-vacia)

((condicion (primero-de lista)) (concatenar (primero-de lista) (filtrar (resto-de lista) condicion)))

(else (filtrar (resto-de lista) condicion))))

(filtrar ‘(1 4) (lambda (x) (< x 3)))

—> ‘(1)

(define smaller-than-three (lambda (x) (< x 3)))

(filtrar ‘(1 4) smaller-than-three)

—> ‘(1)

(define (smaller-than n) (lambda (x) (< x n)))

(filtrar ‘(1 4) (smaller-than 3))

—> ‘(1)

Lambda Functions

Meta-Circular

Meta-Circular

Meta-Circular

Meta-Circular

Meta-Circular

Dynamic! - REPL

What is Object Oriented Programming?

Alan Kay

Dynabook (1970)

I invented the term

Object-Oriented and I

can tell you I did not

have C++ in mind.

Java and C++ make you think that the new ideas are like the old ones. Java is the most distressing thing to hit computing since MS-DOS

What is Object Oriented?

• MUST• Everything is an Object (data is an object, code is an object, classes are

objects, everything is an object!)

• Computation is done sending messages

• EITHER OR BOTH• Classes and Sub classification as means of knowledge organization

• Objects as prototypes as means of knowledge organization

• REALLY NICE TO HAVE • Immediate feedback

• Completely Reflective Environment (Meta-Circular)

Dynamic! More than REPL, Inspectors!

What OO is not• Data types - int, long, double, etc. They are not objects

• Statements - for, while, if, etc. They are not messages

• Static methods - There is no “self/this” on static methods

• Final/Seal methods – There is no message send when used

• When ”code” is not an Object – No Closure or no Lambda, i.e. Java previous 1.8

• JEE is no OO, it is structured programming in Java

• Anemic classes is not OO (Services with DTO, etc)

• Use of Inheritance for Code reuse is not good OO (i.e. ActiveRecord , white box frameworks, etc)

• Dependency Injection abuse is not OO

• IoC abuse is not OO

This is not OO – Filter in Java

What is Functional Programming?

Wikipedia’s definition• […] treats computation as the evaluation of mathematical functions

and avoids changing-state and mutable data.

• It is a declarative programming paradigm, which means programming is done with expressions[…]instead of statements.

• Missing concepts from Wikipedia:• Lambda functions (which allow High Order functions)• Runtime support for recursive implementations (aka: tail recursion

elimination)

• Arguable: • Lazy evaluation (more or less)• Macro

Good OO Design favors Immutable Objects!

This is not OO!

This IS OO!

Real OO Languages represent “Code” as an object

(Closure High Order Functions)• Smalltalk since the ‘70s

• ”Closures got famous because Java don’t have them” (Anonymous)

Some conclusions - Good OO implies:

• Immutable objects when representing immutable entities

• Closure “High order functions”

• Message sending all the way (expressions)

• Consistency (everything is an object)

• Knowledge representation and classification(Programs are Models!)

Some conclusions about FP

• It is a mistake to think that FP is going to solve all the software design problems.

• Design are made by humans, not by programming languages(even though they influence design decisions)

• FP will suffer from the same “miss-used” problems as OO suffers now

• FP does not provide a way to organize the knowledge represented in the software data structures are not enough, we know that from Structured Programming

Some conclusions

•OOP vs. FP is an absurd dichotomy

•OOP and FP complement each other

•Do not act as a “Pop Programmer”

From where “language programming paradigms shifts”

will come from?

For sure NOT from

• Performance improvements

• Less verbose languages

• Better type system (other complete topic to discuss)

• It is “normal science” (khun-onian way to say “more of the same”)

They will come from

• Better tools to help human-machine communication

• Better environments to “augment” human intellect

• More dynamic environments to improve immediate feedback

• …

• Let’s see some examples

For a new definition of

Programming Paradigm!

For better tools!

agile software development & services

¡Gracias!