[日本語注釈つき] Deep Dive into Kotlin DSL

https://speakerdeck.com/jmatsu/deep-dive-into-kotlin-dsl の日本語注釈つき

Transcript

1. Deep Dive into Kotlin DSL
   Kotlin Fest 2019 @red_fat_daruma
   

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2. Self Introduction
   Jumpei Matsuda / Daruma / @red_fat_daruma
   ▸ Software Engineer @DeployGate
   ▸ GitHub: jmatsu / Twitter: red_fat_daruma
   ▸ JVM projects : Android apps/SDK, Scala server-
   side and Gradle plugins
   ▸ One of Kotlin users since M10
   2
   M10 Ҏདྷͷ Kotlin Ϣʔβʔ
   

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3. Today's Goal
   Hopefully, Every Audience Will....
   ▸ Know what is DSL and/or Kotlin DSL
   ▸ Understand what specifications/features of Kotlin support Kotlin DSL
   ▸ Have a motivation to develop the original Kotlin DSL and/or extend
   existing libraries through Kotlin DSL.
   3
   DSL ͱ͸Կ͔ɺKotlin DSL ͱ͸Կ͔Λ஌Δ
   ͲΜͳ࢓༷/ػೳ͕ Kotlin DSL Λࢧ͍͑ͯΔͷ͔ཧղ͢Δ
   ಠࣗͷ Kotlin DSL ͷ࡞੒΍طଘϥΠϒϥϦΛ Kotlin DSL Ͱ֦ு͢ΔϞνϕʔγϣϯΛಘΔ
   ͜ͷൃදΛฉ͍ͨਓ͕ͨͪɺ
   ͱ͍͍ͳ͊
   

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4. Let me ask questions!
   4
   

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5. Who thinks Kotlin DSL
   is for Gradle? ✋
   5
   Kotlin DSL == Gradle ͷ΋ͷͩͱࢥ͍ͬͯΔਓʁ
   

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6. I do not use a word *Kotlin DSL* to represent Kotlin DSL for Gradle
   Kotlin DSL Is Not Only Kotlin DSL for Gradle
   ▸ *Kotlin DSL* in this presentation does not mean Gradle's one
   ▸ Kotlin DSL for Gradle is just a DSL in Kotlin for Gradle
   ▸ Contracts, coroutines, etc. are also Kotlin DSL
   6
   Kotlin DSL ͸ Kotlin DSL for Gradle ͷ͜ͱ͚ͩ͡Όͳ͍
   ͜ͷൃදͰͷ Kotlin DSL ͸ Gradle ͷ΋ͷ͚ͩΛࢦ͢Θ͚͡Όͳ͍
   Kotlin DSL for Gradle ͸ Kotlin Ͱॻ͔Εͨ Gradle ༻ͷ DSL Ͱ͋Δͱ͍͏͚ͩ
   Contracts, coroutines ͱ͔΋ Kotlin DSL
   

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7. I do not use a word *Kotlin DSL* to represent Kotlin DSL for Gradle
   Kotlin DSL Is Not Only Kotlin DSL for Gradle
   ▸ *Kotlin DSL* in this presentation does not mean Gradle's one
   ▸ Kotlin DSL for Gradle is just a DSL in Kotlin for Gradle
   7
   Go to Next questions!
   

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8. Who have used and/or
   are using Kotlin DSL? ✋
   8
   ࠓ·Ͱʹ Kotlin DSL ࢖ͬͨΑɺࠓ΋࢖ͬͯΔΑɺͬͯਓʁ
   

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9. Who know what techniques
   will help Kotlin DSL? ✋
   9
   ͲΜͳٕज़͕ Kotlin DSL Λࢧ͑ͯΔ͔஌ͬͯΔਓʁ
   

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10. Who can explain
    the definition of Kotlin DSL? ✋
    10
    Kotlin DSL ͷఆٛΛઆ໌Ͱ͖Δͻͱ?
    

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11. Who can explain
    the definition of DSL? ✋
    11
    DSL ͷఆٛΛઆ໌Ͱ͖Δͻͱʁ
    

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12. If you said YES to all questions,
    you are already Kotlin DSL deep diver!
    12
    શ෦ͷ࣭໰ʹʮ͸͍ʯͱճ౴Ͱ͖ͨํ͸΋͏͢Ͱʹ Kotlin DSL Deep diver Ͱ͢ɾɾɾ
    

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13. Today's topics
    Agenda
    ▸ The base knowledge of DSL
    ▸ Specifications/techniques of Kotlin DSL based on levels
    ▸ Quick tips for DSL development
    13
    DSL ʹؔ͢Δجૅ஌ࣝ
    Kotlin DSL ͷ࢓༷΍ٕज़ΛϨϕϧผͰ
    DSL ։ൃͷͨΊͷͪΐͬͱͨ͠ tips
    

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14. The base knowledges of DSL
    Domain Specific Language
    ▸ A computer language specialized to a particular application domain
    ▸ In contrast: a general purpose language like Kotlin, Java
    14
    ref: https://en.wikipedia.org/wiki/Domain-specific_language
    υϝΠϯݻ༗ݴޠ
    ಛఆͷΞϓϦέʔγϣϯυϝΠϯʹಛԽͨ͠ίϯϐϡʔλݴޠ
    ରরతͳ΋ͷ͸ Kotlin, Java ͷΑ͏ͳ൚༻ݴޠ
    

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15. Domain Specific Language
    ▸ A computer language specialized to a particular application domain
    ▸ In contrast: a general purpose language like Kotlin, Java
    ▸ What's a motivation to introduce/need DSL?
    15
    The base knowledges of DSL
    ref: https://en.wikipedia.org/wiki/Domain-specific_language
    DSL Λಋೖ͢Δɺඞཁͱ͢ΔϞνϕʔγϣϯ͸ͳʹ͔
    

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16. Why People Want To Use DSL
    ▸ Simplify complex code
    ▸ More readable, understandable, fluent
    ▸ Use smart and/or minimum APIs for the domain
    ▸ Improve productivity and reduce human errors
    ▸ Get a power of type system etc.
    16
    The base knowledges of DSL
    ͳΜͰ DSL Λ࢖͏ͷ͔
    ෳࡶͳίʔυΛγϯϓϧʹ͢ΔͨΊ
    ಡΈ΍͍͢ɺཧղ͠΍͍͢ɺྲྀெͳ interface ΁
    ಛఆυϝΠϯʹର͢ΔεϚʔτͰɺඞཁ࠷௿ݶͳ API ͕ར༻Ͱ͖Δ
    ੜ࢈ੑͷ޲্΍ώϡʔϚϯΤϥʔͷݮগͷͨΊ
    ܕγεςϜͷྗΛಘͨΓͩͱ͔
    

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17. Why People Want To Use DSL
    17
    The base knowledges of DSL
    
    NOTE: pseudo code
    DSL
    ٖࣅίʔυ
    

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18. Aspects of Domain Specific Language
    ▸ External DSL and Internal DSL
    ▸ External: A language that's parsed independently of the host general purpose
    language
    ▸ Internal: A particular form of API in the host general purpose language for the
    domain
    18
    The base knowledges of DSL
    ref: https://martinfowler.com/books/dsl.html
    υϝΠϯݻ༗ݴޠಛੑ
    ֎෦ DSL ͱ಺෦DSL
    ϗετͱͳΔ൚༻ݴޠͱ͸ಠཱͯ͠ύʔε͞ΕΔ DSL
    ϗετͱͳΔ൚༻ݴޠͷதͰɺಛఆͷ API ͷܗࣜΛఏڙ͢Δ DSL
    

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19. Examples in the Real World
    ▸ External DSL
    ▸ SQL, CSS, Regular expressions
    ▸ Internal DSL
    ▸ HTML, Mock Libraries, DI container
    19
    The base knowledges of DSL
    ࣮ྫ
    SQL, CSS, ਖ਼نදݱ
    HTML, ϞοΫϥΠϒϥϦɺDI
    

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20. Examples in the Real World
    ▸ External DSL
    ▸ SQL, CSS, Regular expressions
    ▸ Internal DSL
    ▸ HTML, Mocking Libraries, DI container
    ▸ Kotlin DSL
    20
    The base knowledges of DSL
    

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21. Examples in the Real World
    ▸ External DSL
    ▸ SQL, CSS, Regular expressions
    ▸ Internal DSL
    ▸ HTML, Mocking Libraries, DI container
    ▸ Kotlin DSL
    ▸ NOT a special edition of Kotlin
    21
    The base knowledges of DSL
    Kotlin ͷಛผͳ೿ੜͱ͔͍͏Θ͚Ͱ͸ͳ͍
    

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22. Techniques for Internal DSL Depends on...
    ▸ The host general purpose language
    ▸ Type checking
    ▸ Syntax
    ▸ Syntactic extensions
    ▸ Compiler extensibility and interpolation
    22
    The base knowledges of DSL
    ಺෦ DSL Λࢧ͑Δٕज़͸ҎԼʹґଘ
    ϗετͱͳΔ൚༻ݴޠ
    ܕݕࠪ
    جૅߏจ
    ߏจ֦ு
    ίϯύΠϥ֦ுੑ΍ิؒࢠ
    

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23. Techniques for Internal Kotlin DSL Depends on...
    ▸ A general purpose language Kotlin
    ▸ Type checking Static type checking
    ▸ Syntax Lambda expressions, etc.
    ▸ Syntactic extensions Method extension, operator overloading, etc.
    ▸ Compiler extensibility and/or interpolation Compiler plugins etc.
    23
    The base knowledges of DSL
    

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24. e.g. kotlinx.html is one of Kotlin DSL
    ▸ DSL for HTML domain
    ▸ Generate DOM tree from a Kotlin code
    24
    The base knowledges of DSL
    https://github.com/Kotlin/kotlinx.html
    

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25. e.g. kotlinx.html is one of Kotlin DSL
    ▸ DSL for HTML domain
    ▸ Generate DOM tree from a Kotlin code
    25
    Type safe builder pattern, lambda expressions,
    functions with receiver, higher-order functions,
    operator overloading, DSLMarker, etc.
    The base knowledges of DSL
    

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26. Today's topics
    Agenda
    ▸ The base knowledge of DSL
    ▸ Specifications/techniques of Kotlin DSL based on levels
    ▸ Quick tips for DSL development
    26
    ▸ NOTE: DSL in following slides means Internal DSL unless specified
    Kotlin DSL ͷ࢓༷΍ٕज़ΛϨϕϧผͰ
    DSL ։ൃͷͨΊͷͪΐͬͱͨ͠ tips
    ͔ͬ͜Β໌هͳ͘ DSL ͱ͍ͬͨΒ಺෦ DSL Ͱ͢
    

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27. Techniques of Kotlin DSL
    Techniques of Kotlin DSL
    ▸ Getting started
    ▸ Language specifications
    ▸ Intermediate
    ▸ Features for syntactic extensions
    ▸ Expertise
    ▸ Build environment stuff of Kotlin
    27
    ॳڃ
    தڃ
    ্ڃ
    

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28. Techniques of Kotlin DSL
    ▸ Getting started
    ▸ Language specifications
    ▸ Intermediate
    ▸ Features for syntactic extensions
    ▸ Expertise
    ▸ Build environment stuff of Kotlin
    28
    Techniques of Kotlin DSL - Getting Started
    ݴޠ࢓༷
    

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29. Language Specifications
    ▸ Type system
    ▸ Static type checking
    ▸ Syntax related specifications
    ▸ Lambdas, Functions literals with receiver
    29
    Techniques of Kotlin DSL - Getting Started
    ܕγεςϜ
    ੩తܕݕࠪ
    ߏจʹؔ͢Δ࢓༷
    ϥϜμࣜɺϨγʔό͖ͭؔ਺Ϧςϥϧ
    

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30. Static Type Checking
    ▸ Code analysis based type safety verification
    ▸ In contrast: Dynamic type checking
    ▸ Allow know type violations before executing
    30
    Techniques of Kotlin DSL - Getting Started - 1/3
    ίʔυղੳϕʔεͷܕ҆શੑݕࠪ
    ରর : ಈతܕݕࠪ
    ࣮ߦલʹܕҧ൓Λ஌Δ͜ͱ͕Ͱ͖Δ
    

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31. Static Type Checking
    ▸ Code analysis based type safety verification
    ▸ In contrast: Dynamic type checking
    ▸ Allow know type violations before executing
    31
    Groovy : no error but fail at runtime
    Techniques of Kotlin DSL - Getting Started - 1/3
    Τϥʔ͸ͳ͍͕ɺ࣮ߦ࣌ʹམͪΔ
    ίʔυղੳϕʔεͷܕ҆શੑݕࠪ
    ରর : ಈతܕݕࠪ
    ࣮ߦલʹܕҧ൓Λ஌Δ͜ͱ͕Ͱ͖Δ
    

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32. Static Type Checking
    ▸ Code analysis based type safety verification
    ▸ In contrast: Dynamic type checking
    ▸ Allow know type violations before executing
    32
    Groovy : no error but fail at runtime Kotlin : a compilation error
    Techniques of Kotlin DSL - Getting Started - 1/3
    ίϯύΠϧΤϥʔ
    Τϥʔ͸ͳ͍͕ɺ࣮ߦ࣌ʹམͪΔ
    ίʔυղੳϕʔεͷܕ҆શੑݕࠪ
    ରর : ಈతܕݕࠪ
    ࣮ߦલʹܕҧ൓Λ஌Δ͜ͱ͕Ͱ͖Δ
    

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33. Syntax-Related Specifications
    ▸ Lambda expressions
    ▸ Function literals with receiver
    33
    Techniques of Kotlin DSL - Getting Started - 1.5/3
    ϥϜμࣜ
    Ϩγʔό͖ͭؔ਺Ϧςϥϧ
    

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34. Lambda Expressions
    ▸ Syntax sugar for function type variables and SAM
    ▸ Represent a function by braces
    34
    Techniques of Kotlin DSL - Getting Started - 2/3
    ؔ਺ܕม਺΍ SAM (Single abstract method) ͷ౶ҥߏจ
    தׅހͰؔ਺ΛදݱͰ͖Δ
    

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35. Lambda Expressions - Example
    35
    Techniques of Kotlin DSL - Getting Started - 2/3
    

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36. Lambda Expressions - Example
    36
    Techniques of Kotlin DSL - Getting Started - 2/3
    

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37. Lambda Expressions - Example
    37
    Techniques of Kotlin DSL - Getting Started - 2/3
    

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38. Lambda Expressions - Example
    38
    Techniques of Kotlin DSL - Getting Started - 2/3
    

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39. Lambda Expressions - Example
    39
    Techniques of Kotlin DSL - Getting Started - 2/3
    

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40. Function Literals With Receiver
    ▸ Kotlin allows specify what is this scope of a function
    ▸ Groovy also can do this but Java cannot.
    ▸ Function Type : Receiver.(Argument) -> Return
    ▸ Great help for block-code and fluent style coding
    40
    Techniques of Kotlin DSL - Getting Started - 3/3
    ؔ਺ͷ this είʔϓ(receiver)Λࢦఆ͢Δ͜ͱ͕Ͱ͖Δ
    e.g. Groovy ͸Ͱ͖Δ͚ͲɺJava ͸Ͱ͖ͳ͍
    ؔ਺ܕදه
    ϒϩοΫίʔυදݱ΍ྲྀெͳදݱʹศར
    

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41. Function Literals With Receiver
    41
    Techniques of Kotlin DSL - Getting Started - 3/3
    

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42. A Primitive Kotlin DSL
    ▸ Techniques described before allow create a simple DSL
    42
    Techniques of Kotlin DSL - Getting Started - Closing
    ͜͜·ͰͷςΫχοΫͰγϯϓϧͳ DSL ͸࡞Δ͜ͱ͕Ͱ͖Δ
    ݪ࢝తͳ Kotlin DSL
    

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43. A Primitive Kotlin DSL - Is It Enough for Your Better Development?
    ▸ Only techniques described before allow create a simple DSL
    43
    Techniques of Kotlin DSL - Getting Started - Closing
    ྑ͍։ൃͷͨΊʹ͸͜ΕͰे෼ͩΖ͏͔
    

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44. Break
    ▸ We can build DSLs easily from scratch with knowledges I have explained
    ▸ It's enough if you want type-safe and/or lambda's elegant style.
    ▸ Let's check what techniques can improve usability of Kotlin DSL and how
    we can create Kotlin DSL for existing libraries/APIs.
    44
    Techniques of Kotlin DSL - Getting Started - Closing
    ࠓ·Ͱͷ஌ࣝͰɺεΫϥον͔Β؆୯ʹ DSL ͸࡞ΕΔ
    ܕ҆શͰ͋ͬͨΓɺϥϜμࣜʹΑΔελΠϧͰॻ͖͍͚ͨͩͳΒे෼
    

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45. Break
    ▸ We can build DSLs easily from scratch with knowledges I have explained
    ▸ It's enough if you want type-safe and/or lambda's elegant style.
    ▸ Let's check what techniques can improve usability of Kotlin DSL and how
    we can create Kotlin DSL for existing libraries/APIs.
    45
    Techniques of Kotlin DSL - Getting Started - Closing
    Ͱ͸ͲΜͳςΫχοΫ͕ Kotlin DSL ͷརศੑ΍දݱྗΛ͋͛Δ͔ɺͲ͏΍ͬͯ Kotlin DSL Λ࡞͍͚ͬͯΔͷ͔ΛݟͯΈ·͠ΐ͏
    

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46. Techniques of Kotlin DSL
    ▸ Getting started
    ▸ Language specifications
    ▸ Intermediate
    ▸ Features for syntactic extensions
    ▸ Expertise
    ▸ Build environment stuff of Kotlin
    46
    Techniques of Kotlin DSL - Intermediate
    தڃ
    ߏจ֦ுͷػೳ
    

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47. Syntactic Extension
    ▸ Extension method
    ▸ Operator overloading
    ▸ Infix notation
    ▸ Method convention
    ▸ Delegation
    47
    Techniques of Kotlin DSL - Intermediate - 0/5
    ֦ுؔ਺
    ԋࢉࢠΦʔόʔϩʔυ
    தஔه๏
    ϝιουن໿
    ҕৡ
    

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48. Syntactic Extension
    ▸ Extension method
    ▸ Operator overloading
    ▸ Infix notation
    ▸ Method convention
    ▸ Delegations
    48
    Techniques of Kotlin DSL - Intermediate - 1/5
    ֦ுؔ਺
    

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49. Extension Method
    ▸ Define new member methods w/o inheritances
    ▸ However, we cannot avoid member visibility restrictions
    ▸ The benefits of Extension Method for DSL
    ▸ Can apply the techniques which I will explain later
    ▸ Can create DSLs without modifying 3rd party libraries
    49
    Techniques of Kotlin DSL - Intermediate - 1/5
    ܧঝͳ͠ʹ৽͍͠ϝϯόʔϝιουΛఆٛͰ͖Δ
    ͨͩ͠ϝϯόʔՄࢹੑ͸ӽ͑ΒΕͳ͍
    ར఺ for DSL
    ͜ͷ͋ͱઆ໌͢ΔςΫχοΫΛ͋ͱ͔Βద༻͢Δ͜ͱ͕Ͱ͖Δ
    3rd party ϥΠϒϥϦΛमਖ਼ͤͣʹ DSL ΛߏஙͰ͖Δ
    

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50. Syntactic Extension
    ▸ Extension method
    ▸ Operator overloading
    ▸ Infix notation
    ▸ Method convention
    ▸ Delegations
    50
    Techniques of Kotlin DSL - Intermediate - 2/5
    ԋࢉࢠΦʔόʔϩʔυ
    

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51. Example - kotlinx.html - DOM tree generator in Kotlin
    ▸ + would become a text node
    51
    Techniques of Kotlin DSL - Intermediate - 2/5
    https://github.com/Kotlin/kotlinx.html
    + ͷه๏ͰςΩετϊʔυΛ࡞੒Ͱ͖Δ
    

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52. Example - kotlinx.html - DOM tree generator in Kotlin
    ▸ +"any text" means appending text to the node
    ▸ + is shorter than *text*
    52
    Techniques of Kotlin DSL - Intermediate - 2/5
    https://github.com/Kotlin/kotlinx.html
    + ͱ͍͏ه๏ͦͷ΋ͷ͕ϊʔυ΁ͷςΩετ௥Ճͱ͍͏ૢ࡞Λද͍ͤͯΔ
    + ͸ text ΑΓ type ਺͕গͳ͍
    

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53. Operator Overloading
    ▸ Kotlin allow overload operators for developers
    ▸ We can assign a logic to several operators like +, -...
    ▸ The benefits of Operator Overloading for DSL
    ▸ Basically, operators are shorter than method names
    ▸ A meaning of an operation is clear
    53
    Techniques of Kotlin DSL - Intermediate - 2/5
    ։ൃऀ͸ԋࢉࢠΛΦʔόʔϩʔυ͢Δ͜ͱ͕Ͱ͖Δ
    ͭ·ΓɺಠࣗͷϩδοΫΛطଘͷԋࢉࢠʹ͕͋ͯ͑Δ
    རӹ for DSL
    ͍͍ͩͨͷέʔεͰԋࢉࢠͷํ͕ϝιου໊ΑΓ୹ͯ͘ࡁΉ
    ԋࢉࢠ͔Β͘Δૢ࡞ͷҙຯ͕໌ྎ
    

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54. Syntactic Extension
    ▸ Extension method
    ▸ Operator overloading
    ▸ Infix notation
    ▸ Method convention
    ▸ Delegations
    54
    Techniques of Kotlin DSL - Intermediate - 3/5
    தஔه๏
    

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55. Example - DSL for Hamcrest API
    ▸ Not fluent
    ▸ It might be unclear for non-hamcrest users
    55
    Techniques of Kotlin DSL - Intermediate - 3/5
    ྲྀெͰͳ͍ɺ͗ͪ͜ͳ͍
    Hamcrest ͷϢʔβʔҎ֎ʹ͸΍΍ෆ໌ྎ
    

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56. Example - DSL for Hamcrest API
    ▸ Looks fluent
    ▸ Hamcrest's knowledge is not required
    56
    Techniques of Kotlin DSL - Intermediate - 3/5
    ࣗવݴޠʹ͍ۙɺྲྀெ
    Hamcrest ͷυϝΠϯ஌͕͍ࣝΒͳ͍
    

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57. Infix Notation
    ▸ Allow call a function like *Receiver infix-function argument*
    ▸ Can omit a dot and parentheses from a method call
    ▸ The benefits of Infix Notation for DSL
    ▸ Would be more fluent style
    ▸ Can reduce domain knowledge
    57
    Techniques of Kotlin DSL - Intermediate - 3/5
    Recever infix-function argument ͷܗͰݺͼग़͕͠Մೳ
    υοτ΍ׅހΛলུͯ͠ϝιουίʔϧͰ͖Δ
    རӹ for DSL
    ΋ͬͱྲྀெͳදݱΛ௥ٻͰ͖Δ
    υϝΠϯ஌ࣝΛinterface͔ΒݮΒ͢͜ͱ͕Ͱ͖Δ
    

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58. Syntactic Extension
    ▸ Extension method
    ▸ Operator overloading
    ▸ Infix notation
    ▸ Method convention
    ▸ Delegations
    58
    Techniques of Kotlin DSL - Intermediate - 4/5
    ϝιουن໿
    

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59. Example - Kotlin DSL for Gradle
    ▸ debug is not an existing function which accepts closure
    ▸ It's dynamically generated and be configured by a passed closure
    59
    Techniques of Kotlin DSL - Intermediate - 4/5
    Groovy code
    https://github.com/gradle/gradle
    debug ͸ΫϩʔδϟΛड͚औΔΑ͏ͳطଘͷؔ਺Ͱ͸ͳ͍
    ಈతʹੜ੒͞Εɺ౉͞ΕͨΫϩʔδϟΛݩʹઃఆ͞ΕΔ
    

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60. Example - Kotlin DSL for Gradle
    ▸ NOTE: create(String) creates a configurable object for SigningConfig
    ▸ Prob.: configure is domain knowledge but hidden in Groovy DSL
    60
    Techniques of Kotlin DSL - Intermediate - 4/5
    Groovy code Raw Kotlin code
    https://github.com/gradle/gradle
    NOTE: create(String) ͸ ߏ੒ՄೳͳΦϒδΣΫτΛฦ͢
    configure ؔ਺͸υϝΠϯ஌͕ࣝͩɺGroovy DSL Ͱ͸Ӆ͞Ε͍ͯΔͱ͍͏໰୊఺
    

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61. Example - Kotlin DSL for Gradle
    ▸ Implement an invoke function which accepts a lambda
    ▸ Could hide configure from Kotlin DSL users
    61
    Techniques of Kotlin DSL - Intermediate - 4/5
    https://github.com/gradle/gradle/blob/90974be832395cd5eabff97c18842791d7bee3a8/subprojects/kotlin-dsl/src/main/kotlin/org/gradle/kotlin/dsl/
    NamedDomainObjectContainerExtensions.kt#L36
    https://github.com/gradle/gradle
    ϥϜμΛड͚औΕΔ invoke ؔ਺Λఆٛ͢Δ
    configure Λ Kotlin DSL users ͔ΒӅͤΔ
    

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62. Method Convention
    ▸ This is a kind of operator overloading
    ▸ Operators/syntax which Java does not implement manually will be
    available if a method satisfies a convention
    ▸ Index-access, invoke, range operator...
    ▸ The benefits of Method Convention for DSL
    ▸ Easy to create lambda expressions-based builder by overloading invoke
    ▸ Can hide domain knowledge bypass a common operator/syntax in Kotlin
    62
    Techniques of Kotlin DSL - Intermediate - 4/5
    ԋࢉࢠΦʔόʔϩʔυͷҰछ
    ϝιου͕ن໿Λຬͨ͢͜ͱͰɺJava ͕ಠࣗͰ͸ఆٛͰ͖ͳ͍Α͏ͳԋࢉࢠ΍ߏจ͕࢖͑ΔΑ͏ʹͳΔ
    IndexϕʔεͷΞΫηεɺinvokeɺൣғԋࢉࢠ
    རӹ for DSL
    invoke Λఆٛ͢Δ͜ͱͰɺϥϜμࣜϕʔε(ϒϩοΫίʔυ)ͷϏϧμʔͳͲ͕࡞Γ΍͍͢
    Kotlin Ͱ͸Α͘࢖ΘΕΔԋࢉࢠ΍ߏจͷதʹɺυϝΠϯ஌ࣝΛӅṭ͢Δ͜ͱ͕Ͱ͖Δ
    

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63. Syntactic Extension
    ▸ Extension method
    ▸ Operator overloading
    ▸ Infix notation
    ▸ Method convention
    ▸ Delegation
    63
    Techniques of Kotlin DSL - Intermediate - 5/5
    ҕৡ
    

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64. Example - Kotpref - Android SharedPreferences DSL
    ▸ SharedPreferences API is low-level
    ▸ A simple command-query API sequence is required
    64
    Techniques of Kotlin DSL - Intermediate - 5/5
    https://github.com/chibatching/Kotpref
    SharedPreferences API ͸௿ڃ
    ୯७ͳίϚϯυΫΤϦAPI Λॱ൪ʹୟ͘ඞཁ͕͋Δ
    

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65. Example - Kotpref - Android SharedPreferences DSL
    ▸ Hide low-level API and domain knowledge
    ▸ Writing a value to a property will save it to the preferences but it's hidden
    65
    Techniques of Kotlin DSL - Intermediate - 5/5
    https://github.com/chibatching/Kotpref
    https://github.com/chibatching/Kotpref
    ௿ڃ API ΍υϝΠϯ஌ࣝΛӅͤΔ
    ྫ͑͹propertyʹ஋Λ୅ೖ͢Δͱ SharedPreferences ʹॻ͖ࠐΉ͕ɺͦͷϩδοΫ͸׬શʹӅṭ͞Ε͍ͯΔ
    

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66. Delegation
    ▸ A property delegates to another object when accessed
    ▸ The benefits of Delegations for DSL
    ▸ Can hide domain knowledge
    ▸ Effective for DRY when using read and write operations to properties
    66
    Techniques of Kotlin DSL - Intermediate - 5/5
    ϓϩϖςΟ͸ΞΫηε͞ΕͨΒଞͷΦϒδΣΫτʹॲཧΛҕৡ͢Δ
    རӹ for DSL
    υϝΠϯ஌ࣝΛӅͤΔ
    ϓϩύςΟʹର͢ΔಡΈॻ͖ૢ࡞ʹؔ͢Δ DRY ʹศར
    

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67. Techniques of Kotlin DSL
    ▸ Getting started
    ▸ Language specifications
    ▸ Intermediate
    ▸ Features for syntactic extensions
    ▸ Expertise
    ▸ Build environment stuff of Kotlin
    67
    Techniques of Kotlin DSL - Expertise
    ্ڃ
    Ϗϧυ؀ڥͱ͔
    

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68. Build Environment Stuff of Kotlin
    ▸ The plugin system for the compiler
    ▸ SAM with receiver compiler plugin
    ▸ Interpolators
    ▸ DslMarker
    68
    Techniques of Kotlin DSL - Expertise - 0/2
    ίϯύΠϥͷͨΊͷϓϥάΠϯγεςϜ
    SAM-with-receiver ίϯύΠϥϓϥάΠϯ
    ิؒࢠ
    

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69. Build Environment Stuff of Kotlin
    ▸ The plugin system for the compiler
    ▸ SAM with receiver compiler plugin
    ▸ Interpolators
    ▸ DslMarker
    69
    Techniques of Kotlin DSL - Expertise - 1/2
    

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70. Example - Kotlin DSL for Java Code
    ▸ Java cannot specify a receiver of SAM so Kotlin cannot use functions with
    receiver without extension methods
    70
    Java code Call Container#execute from Kotlin
    Techniques of Kotlin DSL - Expertise - 1/2
    Java ͸ SAM ͷϨγʔόΛࢦఆͰ͖ͳ͍ɻͦͷͨΊ Kotlin ͸Ϩγʔό͖ͭؔ਺Λͦͷ··(֦ுؔ਺ͳ͠)Ͱ͸ѻ͏͜ͱ͕Ͱ͖ͳ͍ɻ
    

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71. ▸ Just annotate SAM interfaces and register the annotation to the plugin
    ▸ An argument of SAM will be a receiver in Kotlin!
    71
    Techniques of Kotlin DSL - Expertise - 1/2
    Example - Kotlin DSL for Java Code
    SAM interface ʹΞϊςʔγϣϯ͚ͭͯɺϓϥάΠϯʹ͓஌Βͤ͢Δ͚ͩ
    SAM ͷҾ਺͕ Kotlin Ͱ͸Ϩγʔόʔʹ
    

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72. SAM With Receiver
    ▸ Control a receiver in SAM conversions
    ▸ For Kotlin code, but need to modify Java code
    ▸ The benefits of SAM-with-receiver
    ▸ Useful when non-Kotlin libraries assume usability of Kotlin DSL
    ▸ Avoid a bit awkward API in Kotlin
    72
    Techniques of Kotlin DSL - Expertise - 1/2
    https://github.com/JetBrains/kotlin/tree/master/plugins/sam-with-receiver
    SAM ม׵࣌ͷϨγʔόʔΛ͍͡ΕΔ
    Kotlin code ͷͨΊͷػೳ͚ͩͲɺJava ଆΛमਖ਼͢Δඞཁ͕͋Δ
    རӹ for DSL
    Kotlin ͡Όͳ͍ϥΠϒϥϦ͕ Kotlin DSL ͷͨΊͷརศੑΛߟ͑Δͱ͖ʹ༗༻
    Kotlin Ͱͪΐͬͱ͗ͪ͜ͳ͍ײ͡ͷ API ʹͳΔͷΛճආͰ͖Δ
    

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73. SAM With Receiver - Example - Kotlin DSL for Gradle
    ▸ Action API is widely used so SAM-with-receiver is better than extensions
    73
    https://github.com/gradle/gradle/commit/18aebdba33cd9e1be966cc286a11d3ce86a28e4f
    Techniques of Kotlin DSL - Expertise - 1/2
    https://github.com/gradle/gradle
    Action API ͸ΊͬͪΌ࢖ΘΕͯΔͷͰɺSAM-with-receiver ͷํ͕֦ுؔ਺ΑΓྑ͍
    

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74. Build Environment Stuff of Kotlin
    ▸ The plugin system for the compiler
    ▸ SAM with receiver compiler plugin
    ▸ Interpolators
    ▸ DslMarker
    74
    Techniques of Kotlin DSL - Expertise - 1/2
    

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75. Example - Pseudo Dom Tree Builder
    ▸ head tag in head tag should be forbidden!
    75
    Techniques of Kotlin DSL - Expertise - 2/2
    head tag ͷதʹ head tag ͸ஔ͍ͪΌ͍͚ͳ͍
    

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76. ▸ Add an annotation of @DslMarker to receiver classes or superclasses (and
    functions if necessary)
    76
    Techniques of Kotlin DSL - Expertise - 2/2
    Example - Pseudo Dom Tree Builder
    DslMarker ͷΞϊςʔγϣϯΛϨγʔόʔͷΫϥε΍εʔύʔΫϥεʹ͚ͭΔ
    

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77. ▸ Show an error because of implicit receiver violation!
    77
    Techniques of Kotlin DSL - Expertise - 2/2
    Example - Pseudo Dom Tree Builder
    ͢Δͱɺ҉໧తʹղܾ͞ΕͨϨγʔόʔ͕ҧ൓ѻ͍ͱͳͬͯΤϥʔ͕දࣔ͞ΕΔ
    

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78. DslMarker
    ▸ Kotlin's only DSL specific feature as far as I know
    ▸ Add a constraint of a caller scope and can raise errors if invalid
    ▸ The benefits of DslMarker for DSL
    ▸ This is required to make your DSL safe
    ▸ Be developers' help because IntelliJ highlight marked functions
    78
    Techniques of Kotlin DSL - Expertise - 2/2
    ஌ΔݶΓɺKotlin ʹ͓͚Δ DSLಛԽͨ͠།Ұͷػೳ
    ݺͼग़͠ͷείʔϓʹ੍໿Λ͚ͭΔ͜ͱ͕Ͱ͖ͯɺҧ൓ͯͨ͠ΒΤϥʔͱͰ͖Δ
    རӹ for DSL
    DSL ͷ҆શੑΛߴΊΔͨΊʹ͸ඞਢ
    ։ൃऀͷॿ͚ʹͳΔɻIntelliJ ͸ϚʔΫ͞Εͨؔ਺ʹରͯ͠ಠࣗͷϋΠϥΠτΛ͔͚ͯ͘ΕΔ
    

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79. DslMarker - Example - kotlinx.html
    ▸ Of course, kotlinx.html uses DslMarker to build DOM tree correctly
    ▸ html, head, body are marked functions so highlighted
    79
    Techniques of Kotlin DSL - Expertise - 2/2
    kotlinx.html ͸΋ͪΖΜར༻͍ͯͯ͠ɺ͜ΕͰਖ਼͘͠ DOM tree Λ࡞ΕΔΑ͏ʹ͍ͯ͠Δ
    html, head ͱ͔͕ϋΠϥΠτ͞ΕͯΔΑͶ
    

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80. Build Environment Stuff of Kotlin - Limitations
    ▸ Compiler plugin stuff is undocumented
    ▸ Complex logic is hard to be implemented
    ▸ Maintainability...
    ▸ DslMarker needs be annotated to classes, so it's unavailable for existing
    libraries
    80
    Techniques of Kotlin DSL - Expertise - Closing
    ίϯύΠϥʔϓϥάΠϯ͸υΩϡϝϯτ͞Εͯͳ͍
    ੍ݶ
    ෳࡶͳϩδοΫ͸ݫ͍͠
    อकੑΣɾɾɾ
    DslMarker ͸ΫϥεʹΞϊςʔγϣϯΛ͚ͭΔඞཁ͕͋ͬͯɺͭ·ΓطଘϥΠϒϥϦͰ͸࢖͑ͳ͍
    

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81. Quick tips for DSL development
    81
    DSL ։ൃͷͨΊͷͪΐͬͱͨ͠ tips
    

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82. Differences Between API and DSL
    ▸ Technically, nothing special but...
    ▸ The concepts of the interface design are different
    ▸ DSL is focusing on the domain
    ▸ DSL is well-designed API set for the domain but also limited
    ▸ We should not assume DSL can work as general APIs
    82
    Quick Tips 1/4
    ٕज़తʹͳΜ͔ҧ͍ͱ͔͸ͳ͍
    API ͱ DSL ͷҧ͍
    interface ͷઃܭίϯηϓτ͕ҟͳΔ
    DSL ͸υϝΠϯʹॏ͖Λஔ͍ͯΔ
    DSL ͸υϝΠϯʹରͯ͠Α͘࿅ΒΕͨ API ηοτ͚ͩͲɺͦͷ෼੍ݶ΋͋Δ
    DSL ͕൚༻తͳ API ͱͯ͠ಈ͘ͱ૝ఆ͢Δ΂͖Ͱ͸ͳ͍
    

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83. Quick Tips 2/4
    Adapt Kotlin DSL to Existing Libraries
    ▸ Aggregate existing APIs by extension method
    ▸ Use Operator overloading, Infix operators, Method conventions
    ▸ Create DTOs if you would like to use DslMarker
    83
    ֦ுؔ਺Ͱطଘ API Λू໿͢Δͱ͜Ζ͔Βߟ͑Δ
    طଘϥΠϒϥϦ΁ͷ Kotlin DSL ͷద༻
    ԋࢉࢠΦʔόʔϩʔυɺதஔه๏ɺϝιουن໿Λ࢖͍͖ͬͯ·͠ΐ͏
    DslMarker Λ࢖͍͍ͨͳΒࣗલͰ Data transfer object Λ࡞ͬͯରԠ͠·͠ΐ͏
    

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84. Quick Tips 3/4
    How To Keep Both Usabilities of Kotlin DSL and Other JVM Languages
    ▸ Java -> Kotlin DSL
    ▸ Use SAM with receiver
    ▸ Kotlin DSL -> Other JVM languages
    ▸ Provide method chaining interface because of functions with receiver issue
    ▸ Provide alternative non-inline APIs because of inline features' availability
    ▸ Split API for other JVM languages and Kotlin DSL
    84
    Kotlin DSL ΛJava ϥΠϒϥϦʹద༻͢Δέʔε
    Ͳ͏΍ͬͯ Kotlin DSL ͱଞJVMݴޠͱͰརศੑΛҡ࣋͢Δ͔
    ͪΌΜͱ sam-with-receiver Λ࢖͍·͠ΐ͏
    Kotlin DSL ͷ interface ΛଞJVMݴޠ͔Β࢖͏έʔε
    Ϩγʔόʔ͖ͭؔ਺Ϧςϥϧ໰୊͕͋ΔͷͰɺϝιουνΣʔϯࣜͷ interface ͳͲΛผ్༻ҙ͢Δ
    inline ܥػೳͷՄࢹੑ໰୊͕͋ΔͷͰɺinline ͡Όͳ͍ API Λผ్ఏڙ͢Δ
    ଞJVMݴޠ༻్ͷ API ͱ Kotlin DSL ͸෼͚࣮ͯ૷͢Δ
    

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85. Quick Tips 3/4
    How To Keep Both Usabilities of Kotlin DSL and Other JVM Languages
    ▸ Java -> Kotlin DSL
    ▸ Use SAM with receiver
    ▸ Kotlin DSL -> Other JVM languages
    ▸ Provide method chaining interface because of receiver issue
    ▸ Provide alternative non-inline APIs because of inline vibisility
    ▸ Split API for other jvm languages and Kotlin DSL
    ▸ Other JVM languages -> Kotlin DSL : I don't know, sorry
    85
    JavaҎ֎ͷJVMݴޠʹ Kotlin DSL ΛషΔͱ͖ : ͢Έ·ͤΜɺܦݧෆ଍ͰΘ͔Μͳ͍Ͱ͢
    

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86. Quick Tips 4/4
    For Advanced Steps
    ▸ Read Martin Fowler's DSL Patterns if you want to know DSL interfaces
    ▸ Good examples of Kotlin DSL
    ▸ See appendix!
    86
    ͦͷ·ͨઌ΁
    DSL ͷΠϯλʔϑΣʔεʹ͍ͭͯ஌Γ͍ͨ৔߹͸Martin Fowler ͷ DSL ύλʔϯ͸ಡΈ·͠ΐ͏
    Kotlin DSL ͷྑ͍ྫ
    ༨ന͕ͳ͔ͬͨͷͰ Appendix Λݟ͍ͯͩ͘͞
    

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87. Closing
    87
    

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88. Closing
    Summary 1/3
    ▸ Kotlin DSL is
    ▸ A pure Kotlin code
    ▸ Not only for Kotlin libraries
    ▸ Built on several techniques
    88
    ७ਮͳ Kotlin ίʔυ
    Kotlin Ͱॻ͔ΕͨϥΠϒϥϦͷͨΊ͚ͩ͡Όͳ͍Α
    ͍͔ͭ͘ͷٕज़ͷ্ʹ੒ΓཱͬͯΔΑ
    

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89. Summary 2/3
    ▸ Language specs
    ▸ Static type
    ▸ Lambda expressions w/ receiver control
    ▸ Language features
    ▸ Extension method, operator overloading, infix notation, method convention,
    delegation
    ▸ Build environment features
    ▸ SAM-with-receiver, DslMarker
    89
    Closing
    ੩తܕ෇͚
    ϥϜμࣜͱϨγʔόʔͷ؅ཧ
    ݴޠ࢓༷
    ݴޠػೳ
    ֦ுؔ਺ɺԋࢉࢠΦʔόʔϩʔυɺதஔه๏ɺϝιουن໿ɺҕৡ
    Ϗϧυ؀ڥܥ
    

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90. Summary 3/3
    ▸ DslMarker is the only DSL specific feature but improves safety!
    ▸ Kotlin DSL can extend existing libraries with only a few constraints
    ▸ We can co-exist usability for the both of Kotlin and other JVM languages
    ▸ If you work hard
    90
    Closing
    DslMarker ͚͕ͩ Kotlin DSL ༻ͷಛԽػೳɻ҆શੑΛ޲্Ͱ͖Δ(࢖͍·͠ΐ͏)
    Kotlin DSL ͸طଘϥΠϒϥϦΛͪΐͬͱ੍ͨ͠໿͖͚ͭͩͲ֦ுͰ͖Δ
    Kotlin DSL ͱଞJVMݴޠͰͷརศੑ͸ڞଘՄೳ(ͨͩ͠ؤுΕ͹)
    

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91. Appendix 1/2
    ▸ Books
    ▸ Domain Specific Languages by M. Fowler with R. Parsons
    ▸ DSLs in Action by D. Ghosh
    ▸ Dsl Engineering: Designing, Implementing and Using Domain-specific Languages by M. Voelter
    ▸ Kotlin in Action by D. Jemerrov and S. Isakova
    ▸ Web/Blog
    ▸ Catalog of DSL Patterns https://martinfowler.com/dslCatalog/
    ▸ Kotlin DSL: From Theory to Practice https://dzone.com/articles/kotlin-dsl-from-theory-to-practice
    ▸ Writing a Kotlin DSL (series) https://proandroiddev.com/writing-dsls-in-kotlin-part-1-7f5d2193f277
    ▸ Idiomatic Kotlin. Best Practices. https://phauer.com/2017/idiomatic-kotlin-best-practices/
    ▸ and more...
    91
    Closing
    

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92. Appendix 2/2
    ▸ Libraries
    ▸ Build system : gradle/gradle/tree/master/subprojects/kotlin-dsl
    ▸ Android : android-ktx, Jetpack Compose, Kotlin/anko, JakeWharton/kotterknife, chibatching/Kotpref, infotech-group/
    android-drawable-dsl, agoda-com/Kakao
    ▸ Web : Kotlin/kotlinx.html, perwendel/spark-kotlin, spring-projects/spring-fu, ktorio/ktor
    ▸ Testing libraries : MarkusAmshove/Kluent, winterbe/expekt, npryce/hamkrest, nhaarman/mockito-kotlin, kotlintest/
    kotlintest, spekframework/spek
    ▸ DI containers : Kodein-Framework/Kodein-DI, Ekito/koin, authzee/kotlin-guice
    ▸ Otherwise: skrapeit/skrape.it, JetBrains/Exposed, x2bool/kuery, ruslanys/telegraff,
    ▸ Words
    ▸ Kotlin DSL, DSL, kotlish, type builder, kotlinize, idiomatic Kotlin
    92
    Closing
    

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93. Fin.
    Thank You for Listening!
    ▸ Jumpei Matsuda / daruma
    ▸ Software Engineer @DeployGate
    ▸ GitHub: jmatsu
    ▸ Twitter: red_fat_daruma
    ▸ Please feel free to ask questions
    ▸ ೔ຊޠŧŔŕŪũƄŝſ (Ӊ౎ٶҭͪͷ७೔ຊਓͰ͢)
    93
    

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