Rolling Random Romans - Speaker Deck

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ROLLING RANDOM ROMANS

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TAKE A JOURNEY

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REPUBLICAN ROME

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YOU

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JUNO

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YOUR MISSION

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ROMAN NAMING SYSTEM

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MEN

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PRAENOMEN Publius Cornelius Scipio Africanus

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NOMEN Publius Cornelius Scipio Africanus

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COGNOMEN Publius Cornelius Scipio Africanus

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AGNOMEN Publius Cornelius Scipio Africanus

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WOMEN

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NOMEN Cornelia Africana Minor

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COGNOMEN Cornelia Africana Minor

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DIFFERENTIATOR Cornelia Africana Minor

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OUR PROGRAM

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MODEL type alias Id = Integer type alias Model = { romans : Dict Id Roman , nextId : Id }

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ROMAN type alias Roman = { id : Id , clan : Clan , children : Children , name : Name } type Children = Children (List Roman)

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NAME type Name = FemaleName (Maybe String) (Maybe String) | MaleName String (Maybe String) (Maybe String) type alias Clan = { name : String , color : String }

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VIEW viewRoman : Roman -> Html Msg viewRoman roman = li [ style [ ( "color", roman.clan.color ) ] ] [ text (formattedName roman) , button [ onClick (GenerateChildFor roman) ] [ text "Bless with child" ] , viewChildren roman.children ]

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UPDATE type Msg = GenerateChildFor Roman | Birth Roman Roman update : Msg -> Model -> ( Model, Cmd Msg ) update msg model = case msg of GenerateChildFor father -> ( model, Random.generate (Birth father) Random.Roman.roman ) Birth father child -> -- append child to father ( { model | romans = updatedRomans }, Cmd.none )

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RANDOMNESS IN A FUNCTIONAL WORLD

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PURE FUNCTIONS > 2 + 2 = 4 > floor 5.6 = 5 > toUpper "abc" = "ABC"

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RANDOM IS INHERENTLY NOT PURE rand(1000) # => 964 rand(1000) # => 592 rand(1000) # => 482 rand(1000) # => 872 rand(1000) # => 815

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RANDOM AS A PURE FUNCTION def seeded_rand(seed, max) srand(seed) rand(max) end seeded_rand(123, 1000) # => 510 seeded_rand(123, 1000) # => 510 seeded_rand(123, 1000) # => 510 seeded_rand(123, 1000) # => 510 seeded_rand(123, 1000) # => 510

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PSEUDO-RANDOM

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RANDOM IN ELM

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EXPLICIT SEED randomBool : (Bool, Random.Seed) randomBool = Random.step (Random.initialSeed 123) (Random.bool)

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COMMANDS type Msg = RequestRandom | Generated Bool update : Msg -> Model -> (Model, Cmd Msg) update msg model = case msg of RequestRandom -> (model, Random.generate Generated Random.bool) Generated bool -> ({ model | flag = bool }, Cmd.none)

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COMPLEX VALUES roman : Random.Generator Roman roman = -- generator for romans with random -- * praenomen -- * cognomen -- * agnomen -- * differentiator -- * gender

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BUILDING GENERATORS

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WORK FROM THE BOTTOM UP

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USING EXISTING GENERATOR import Random.Extra differentiator : Random.Generator (Maybe String) differentiator = let differentiators = [ "Maior" , "Minor" , "Prima" , "Tertia" ] in Random.Extra.sample differentiators

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TRANSFORMING ROLLED VALUES femaleName : Random.Generator Name femaleName = Random.map (FemaleName Nothing) differentiator

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COMBINING INDEPENDENT ROLLS femaleName : Roman -> Random.Generator Name femaleName father = Random.map2 FemaleName (femaleCognomen father) differentiator

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CHAIN OF DEPENDENCIES

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MALE NAME maleName : Random.Generator Name maleName = Random.map3 MaleName praenomen cognomen agnomen

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AGNOMEN agnomen : Maybe String -> Generator (Maybe String) agnomen cog = case cog of Just _ -> Random.extra.sample ["Felix", "Cuncunctor", "Africanus"] Nothing -> Random.Extra.constant Nothing

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CHAINING DEPENDENT ROLLS import Random exposing(andThen) maleName : Random.Generator Name maleName = Random.map3 MaleName praenomen cognomen (cognomen `andThen` agnomen)

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FIXING A BUG import Random exposing(andThen) maleNameFromCognomen : Maybe String -> Generator Name maleNameFromCognomen cog = Random.map3 MaleName praenomen (Random.Extra.constant cog) (agnomen cog) maleName : Generator Name maleName = cognomen `andThen` maleNameFromCognomen

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RANDOM PLAYBOOK > Existing generators > Transform generators with Random.map > Combine independent generators with Random.map2 and friends > Combine dependent generators with Random.andThen

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Random.Extra elm-community/random-extra

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REMAINING STEPS > Rinse > Repeat > Profit $$$

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EXTRA CREDIT > Some praenomina are favored by a family > Cognomina can be hereditary > weight rolls with percentages

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DEMO TIME https://joelq.github.io/elm-conf-demo

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PRINCIPLES > Take advantage of Commands > Make as few calls to Random.generate as possible > Build up complex generators using map, map2, andThen etc > Build from the bottom up

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ABOUT ME > Twitter: @joelquen > GitHub: @JoelQ > Slides: JoelQ/elm-conf-talk > Demo: JoelQ/elm-conf-demo

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IMAGES CREDITS > Dice Michael and is distributed under the Creative Commons Attribution 4.0 license. > SPQR See page for author [CC BY 3.0 (http:// creativecommons.org/licenses/by/3.0) or Public domain], via Wikimedia Commons > Republican Elephant By Republican Party (United States)

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IMAGE CREDITS (CONTINUED) > Elephants at Zama Henri-Paul Motte [Public domain or Public domain], via Wikimedia Commons > Scipio Africanus Giovanni Battista Tiepolo [Public domain or Public domain], via Wikimedia Commons > Cornelia Africana Laurent de La Hyre [Public domain or