The document discusses functional programming concepts like pure functions, higher order functions, and referential transparency. Pure functions are those whose return value depends only on their input values, without any observable side effects. Higher order functions are functions that take other functions as arguments or return functions. Referential transparency means a function call can be replaced by its return value without changing the program's behavior. The document argues that functional programming benefits include easier debugging, simpler and cleaner code, and increased reusability. While not all programs can be purely functional, its principles can still be applied.

1. Functional Programming
“As simple as it could be”
By: Ayat Khraisat

2. What we are going to discuss?
• We are not going to discuss code.
• What’s pure function is?
• First class citizens, higher order functions.
• Referentially Transparent.
• Functional, Imperative or Reactive.
• Functional benefits.

3. We are not talking about something new

4. Pure Functions
• You are not pure if you changes
with time.
• You are not pure if you changes
you answer.
• You are not pure if you mutate
the system state or any side
effects.
• You not pure if you depends on
global state.

5. Change state produces Bugs
So
Use constants as much as you can.
No statements just expressions. Also as much as you can
No void functions.

6. Higher Order Functions
a function that takes function or returns

7. Function is considered First Class Citizen if it
can assigned to variables or stored in data
structures and and sent/returned from other one.

8. Referentially transparent
There are many ways to REFERENCE that
thing.
You should read “transparent” to mean
“doesn’t make a difference”
A function Referentially transparent
is call to this method may be
replaced by its return value
X= 5+(1+3) or X= 5+4 or X=9

9. Functional does not mean Reactive

10. Functional programming does not conflict with OOP

11. Why Should we change?

12. 1. No Asking what’s is the state? “Easier Debugging”
2. Simpler Easier and more Cleaner.
3. less NPE.
4. Less change state errors.
5. Less Interfaces and delegates.
6. Reusability.
7. You will find more when you start using it.
Functional Programming Benefits

13. No program can be functional forever
“At some point, it needs to be
imperative and spell out to the
computer exactly how to do something,
and it needs to modify state (whether
that is updating a View, writing to the
server, or just printing to console)”

14. What do you think, should we change?