Lightning - Monads you already use (without knowing it)

The lightning talk version of this talk.

Transcript

1. Monads you’ve
   already put in prod
   Tejas Dinkar
   Nilenso Software
   

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2. about.me
   • Hi, I’m Tejas
   • Nilenso: Partner
   • twitter: tdinkar
   • github: gja
   

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3. If you think you understand Monads,
   you don't understand Monads.
   

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4. This talk is inaccurate and will
   make a mathematician cry
   

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5. Monads
   • Programmable Semicolons
   • Used to hide plumbing away from you
   • Monads are just monoids in the category of
   endofunctors
   

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7. Values
   Value
   

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8. Monads
   Value
   Box
   

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9. Monads
   • Monads define two functions
   • return takes a value and puts it in a box
   • bind takes a box & function, and returns a box
   with f(value)
   

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10. Some math
    (√4) + 5
    

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11. Some math
    (√4) + 5
    3 or 7!
    

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12. Value
    4
    

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13. Monad
    [4]
    

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14. return
    def m_return(x)
    [x]
    end
    # m_r(4) => [4]
    

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15. Square Root fn
    def sqrt(x)
    s = Math.sqrt(x)
    [s, -s]
    end
    # sqrt(4) => [2, -2]
    

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16. Bind Function
    x = m_return(4)
    y = ?????(x) { |p|
    sqrt(p)
    }
    # I want [-2, 2]
    

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17. Bind Function
    x = m_return(4)
    y = x.flat_map {|p|
    sqrt(p)
    }
    # y => [2, -2]
    

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18. Increment Fn
    def inc_5(x)
    [x + 5]
    end
    # inc_5(1) => [6]
    

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19. Putting it together
    m_return(4).
    flat_map {|p| sqrt(p)}.
    flat_map {|p| inc_5(p)}
    # => [3, 7]
    

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20. You have invented the
    List Monad, used to
    model non-determinism
    Congrats
    

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