Monad

Just another abstraction

Transcript

1. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   Monad
   March 1, 2014
   Sibi Just Another Abstraction
   

   View Slide

2. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   About Me
   Sibi
   Haskell Programmer
   Internet Handle: psibi (github, Twitter)
   Mail: sibi@psibi.in
   Sibi Just Another Abstraction
   

   View Slide

3. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   Outline
   1 Introduction
   2 Monad
   3 Sheep Cloning Experiment
   4 Conclusion
   Sibi Just Another Abstraction
   

   View Slide

4. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   Some basics
   Types
   TypeClasses
   Functions
   Sibi Just Another Abstraction
   

   View Slide

5. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   Maybe Type
   For values which may or may not have a value.
   data Maybe a = Just a | Nothing
   Examples:
   Just "hi"
   Just 3
   Nothing
   Sibi Just Another Abstraction
   

   View Slide

6. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   Definition
   Category theory definition is scary!
   But you don’t need to know that. :-)
   Best learnt with time and observing patterns.
   Sibi Just Another Abstraction
   

   View Slide

7. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   Monad TypeClass
   class Monad m where
   (>>=) : : m a −> ( a −> m b ) −> m b
   return : : a −> m a
   Sibi Just Another Abstraction
   

   View Slide

8. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   Maybe Monad
   instance Monad Maybe where
   return x = Just x
   Nothing >>= f = Nothing
   Just x >>= f = f x
   Sibi Just Another Abstraction
   

   View Slide

9. Introduction
   Monad
   Sheep Cloning Experiment
   Conclusion
   Types and Functions
   type Sheep = . . .
   father : : Sheep −> Maybe Sheep
   father = . . .
   mother : : Sheep −> Maybe Sheep
   mother = . . .
   Sibi Just Another Abstraction
   

   View Slide

10. Introduction
    Monad
    Sheep Cloning Experiment
    Conclusion
    Other Functions
    maternalGrandfather : : Sheep −> Maybe Sheep
    maternalGrandfather s = case ( mother s ) of
    Nothing −> Nothing
    Just m −> father m
    mpg : : Sheep −> Maybe Sheep
    mpg s = case ( mother s ) of
    Nothing −> Nothing
    Just m −> case ( father m) of
    Nothing −> Nothing
    Just gf −> father gf
    Sibi Just Another Abstraction
    

    View Slide

11. Introduction
    Monad
    Sheep Cloning Experiment
    Conclusion
    Monads into action!
    mpg : : Sheep −> Maybe Sheep
    mpg s = ( Just s ) >>= mother >>= father >>= father
    Sibi Just Another Abstraction
    

    View Slide

12. Introduction
    Monad
    Sheep Cloning Experiment
    Conclusion
    Conclusion
    Monads are easy!
    Monads are fun!
    It’s just another abstraction.
    There are lot of other abstractions. :-)
    Sibi Just Another Abstraction
    

    View Slide

13. Introduction
    Monad
    Sheep Cloning Experiment
    Conclusion
    Courtesy
    All about Monads by Jeff Newbern
    Real World Haskell
    Sibi Just Another Abstraction
    

    View Slide

14. Introduction
    Monad
    Sheep Cloning Experiment
    Conclusion
    Questions?
    ???
    Sibi Just Another Abstraction
    

    View Slide