1. FUNCTIONAL GEEKERY
FOR AN IMPERATIVE MIND
Rajeev N B

2. @rshetty on Github
@rbharshetty on Twitter

4. SIMON PEYTON JONES

5. NIRVANA
C, C++, Java,
Ruby ..
Haskell
Nirvana
Useful
Less
Useful
Unsafe Safe

6. IMPERATIVE VS FUNCTIONAL

7. PROPERTY IMPERATIVE FUNCTIONAL
FOCUS
Changing existing
values
Declaring new values
CONTROL FLOW
Loops, Conditionals
and Function calls
Functional calls
including Recursion
MANIPULATION
UNIT
Instances of classes
and structs
Functions and Data
Structures.
MENTAL MODEL
Algorithmic
Programming
Composing problems
with set of functions.

8. FUNCTIONAL PROGRAMMING?

9. – John Hughes
(Why Functional Programming Matters)
“Functional Programming is so called because a
program consists entirely of functions”

10. CONCEPTS

11. FUNCTION COMPOSITION
(F O G)

12. It is the act of pipelining result of a
function into input of another,
creating a new function

13. Function g(x)
x + 1
Function f(x)
x * x
x = 3
g(x)= 4
f(g(x))= 16

16. It is the act of pipelining result of a
function into input of with another,
creating a new function

20. LAZY EVALUATION

21. Evaluation of a expression is
deferred until the result is needed
by other computations

22. LAZY EVALUATION
Call by need
Infinite Data structures
Thunks
Performant

23. HIGHER ORDER FUNCTIONS

24. Functions which either take functions
as arguments or return functions as
return values

27. CURRYING

28. Transforming function that takes
multiple arguments into function that
takes single argument

31. PURE FUNCTION

32. Function that returns exactly the
same result every time it is called
with same set of arguments

33. Pure Function
f(x) =
Math.cos(x)
Pure Function ( No Side Effects )
x
f(x)

35. REFERENTIALTRANSPARENCY
Expression is referentially transparent if it can be replaced with
its value
Property of Pure functions
No side effects
Easier to reason about programs

36. WHY PURE FUNCTIONS?
Reproducible results
Memoization
Parallelization

37. IMMUTABILITY

38. Immutable object is an object whose
state cannot be modified after it is
created

39. IMMUTABLE DATA STRUCTURES
Data structure once created cannot be modified
Uses sophisticated structure sharing

40. WHY?
Concurrency
Security

41. FUNCTIONALTHINKING

42. REFERENCES
Haskell Wiki
LearnYou a Haskell
Ruby Function Composition
Resurgence of Functional Programming
Code samples

43. THANKS

44. QUESTIONS?