Do or don’t. Try there is not. Or is there? The power of monads explained. Sort of

One of the great things about being a programmer is that you never stop learning. Even after having programmed for almost 35 years, I still improve on the way I write code. Recently the way I write code changed once again when I started to apply monads and especially the Try class.

During a recent project, my team created a small library that ports the behavior of the Scala Try monad. Although at first, this new monad didn't appeal to me, I soon really started to appreciate this style of programming, where we concatenate series of Map() and FlatMap() methods, using lambda’s, and avoiding abundant try-catch blocks, and many if statements and null checks.

In the meantime, I have contaminated many programmers with this style. Developers make it a sport to always start every method with a return statement. During this talk I’ll discuss lambda’s, closures and monads, and demonstrate the power of this simple monad, using many code examples (in Java, C#, and TypeScript). Don't hesitate to join in.

Transcript

1. @aahoogendoorn | Do or don't. Try there is not. Or is there?
   DO OR DON’T. TRY THERE IS NOT.
   OR IS THERE?
   EXPLAINING MONADS. SORT OF.
   

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2. SANDER HOOGENDOORN
   CODE PHILOSOPHER
   Independent dad, speaker, author, traveler
   Freelance CTO, trainer, architect, programmer
   CURRENTLY
   CTO iBood
   [Chief architect Quby]
   Chief Architect MendriX
   BEFORE
   CTO ANVA
   CTO Klaverblad Verzekeringen
   Global agile thought leader Capgemini
   sanderhoogendoorn.com
   aahoogendoorn
   aahoogendoorn
   aahoogendoorn
   sander@ditisagile.nl
   @aahoogendoorn | Do or don't. Try there is not. Or is there?
   

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3. @aahoogendoorn | Do or don't. Try there is not. Or is there?
   WHAT IS A TRY?
   AND WHERE IS THIS TALK GOING TO?
   

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4. @aahoogendoorn | Do or don't. Try there is not. Or is there?
   

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5. @aahoogendoorn | Do or don't. Try there is not. Or is there?
   

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6. INTRODUCTION
   A BRIEF, INCOMPLETE AND
   MOSTLY WRONG HISTORY OF
   PROGRAMMING LANGUAGES
   @aahoogendoorn | Do or don't. Try there is not. Or is there?
   

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7. 1959 - After losing a bet with L. Ron Hubbard,
   Grace Hopper and several other sadists
   invent the Capitalization Of Boilerplate
   Oriented Language (COBOL) .
   Grace Hopper
   COBOL
   @aahoogendoorn | Do or don't. Try there is not. Or is there?
   

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8. @aahoogendoorn | Do or don't. Try there is not. Or is there?
   

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9. 1964 - John Kemeny and Thomas Kurtz
   create BASIC, an unstructured programming
   language for non-computer scientists.
   John Kemeny
   BASIC
   1965 - Kemeny and Kurtz go to 1964.
   @aahoogendoorn | Do or don't. Try there is not. Or is there?
   

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10. 1968 - Go to statement considered harmful
    The go to statement as it stands is just too primitive;
    it is too much an invitation to make a mess of one's
    program.
    Edsger
    Dijkstra
    GOTO
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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11. LAMBDA’S
    THEN
    OK, AND CLOSURES TOO
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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12. 1970 - Guy Steele and Gerald Sussman create
    Scheme. Their work leads to a series of "Lambda the
    Ultimate" papers culminating in "Lambda the
    Ultimate Kitchen Utensil."
    Lambdas are relegated to relative obscurity until Java
    makes them popular by not having them.
    Guy Steele
    LAMBDA’S
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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13. A lambda expression is an anonymous function that you can use
    to create delegates or expression tree types. By using lambda
    expressions, you can write local functions that can be passed as
    arguments or returned as the value of function calls.
    Lambda expressions are particularly helpful for writing LINQ query
    expressions.
    From: C# Programming Guide
    LAMBDA EXPRESSION
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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14. PURE
    FUNCTIONS
    (JUST BRIEFLY, DON’T WORRY)
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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15. 1990 - A committee formed by Simon Peyton-Jones, Paul
    Hudak, Philip Wadler, Ashton Kutcher, and People for the
    Ethical Treatment of Animals creates Haskell, a pure, non-strict,
    functional language.
    Haskell gets some resistance due to the complexity of using
    monads to control side effects. Wadler tries to appease critics
    by explaining that "a monad is a monoid in the category of
    endofunctors, what's the problem?"
    Philip Wadler
    HASKELL
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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16. A pure function is a function where the return value is only
    determined by its input values, without observable side effects.
    This is how functions in math work: Math.cos(x) will, for the same
    value of x, always return the same result.
    Computing it does not change x. It does not write to log files, do
    network requests, ask for user input, or change program state. It’s
    a coffee grinder: beans go in, powder comes out, end of story.
    PURE FUNCTION
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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17. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    IDEMPOTENT FUNCTIONS
    

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18. So if my programming
    language only supports
    pure functions,
    how do I handle
    any side effects?
    Using
    monads?
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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19. TRYING
    TO EXPLAIN
    MONADS
    (TO NON-HASKELL OR F#
    PROGRAMMERS OF COURSE)
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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20. Monads are amazing. They are simple things, almost
    trivially implemented, with enormous power to
    manage complexity.
    But understanding them is surprisingly difficult, and
    most people, once they have that ah-ha moment,
    seem to lose the ability to explain them to others.
    Douglas
    Crockford
    MONADS EXPLAINED…
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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21. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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22. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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23. Unit
    Bind Bind
    Get
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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24. Map( -> ) :
    FlatMap( -> ) :
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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25. MAYBE
    MY FIRST MONAD
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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26. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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27. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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28. The billion-dollar mistake
    In 1965, I was designing the first comprehensive type system
    for references in an object oriented language (ALGOL W). My
    goal was to ensure that all use of references should be
    absolutely safe, with checking performed automatically by the
    compiler.
    But I couldn’t resist the temptation to put in a null reference,
    simply because it was so easy to implement. I call it my billion-
    dollar mistake.
    Tony Hoare
    NULL
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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29. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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30. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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31. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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32. MONADS IN C#
    • SelectMany and LINQ
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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33. MONADS IN C#
    • Task
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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34. MONADS IN JAVASCRIPT / TYPESCRIPT
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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35. MONADS IN JAVASCRIPT / TYPESCRIPT
    • Promise
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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36. MONADS IN JAVA
    • Optional
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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37. CASE
    BUILDING A SIMPLE
    SWITCH MONAD
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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38. BUILDING A SIMPLE SWITCH MONAD
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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39. BUILDING A SIMPLE SWITCH MONAD
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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40. BUILDING A SIMPLE SWITCH MONAD
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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41. THE TRY CLASS
    ONE BAD-ASS MONAD
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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42. 1975 - IF-THEN-ELSE considered harmful
    Although the if-then-else construct for flow of control
    is simple in some senses, and certainly superior to
    unrestricted go to logic, the indefinite replication of
    this structure leads to undesirable program
    constructs.
    Gerald
    Weinberg
    IF
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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43. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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44. TRY
    SUCCESS FAILURE
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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45. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    TRY
    

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46. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    SUCCESS
    

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47. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    FAILURE
    

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48. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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49. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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50. USING TRY MAKES TESTING LIGHTER
    • No need to test for Exceptions or Errors
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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51. TRY IN TYPESCRIPT
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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52. IN
    RETROSPECTIVE
    SOME FINAL THOUGHTS
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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53. WHY MONADS?
    Robust code
    Reduce complexity
    Focus on the real issue
    Hide implementation details
    Remove side effects
    Hardly any try-catch and if-else-then
    blocks
    Reduce duplication of code
    Improved readability of code
    Easier to maintain
    Easier to test, no need to test for side
    effects
    Once you go Try, you never go back
    

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54. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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55. NEVER STOP LEARNING
    BY DOING IT CONTINUOUSLY
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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56. AND NEVER FORGET TO HAVE FUN
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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57. FURTHER READING
    A brief, Incomplete, and Mostly Wrong History of Programming Languages
    http://james-iry.blogspot.nl/2009/05/brief-incomplete-and-mostly-wrong.html
    You Could Have Invented Monads! (And Maybe You Already Have)
    http://blog.sigfpe.com/2006/08/you-could-have-invented-monads-and.html
    Monads explained in C#
    http://mikhail.io/2016/01/monads-explained-in-csharp/
    Monads
    https://ericlippert.com/category/monads/
    Do. Or do not. There's no Try.
    https://github.com/aahoogendoorn/Monads
    There’s tons of category theory, monad, flatMap, pure function, Maybe, Optional, Try explanations
    @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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58. @aahoogendoorn | Do or don't. Try there is not. Or is there?
    

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59. REFERENCES
    AND QUESTIONS
    www.sanderhoogendoorn.com
    aahoogendoorn
    aahoogendoorn
    aahoogendoorn
    sander@ditisagile.nl
    quby.com/careers
    www.sanderhoogendoorn.com/decks-and-handouts
    

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60. SANDER HOOGENDOORN
    www.sanderhoogendoorn.com
    aahoogendoorn
    aahoogendoorn
    aahoogendoorn
    sander@ditisagile.nl
    

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