DSLs

1
DSLs

• Daniel Frey

2
Roadmap

• Introduction
• Definitions
• Pros/Cons
• Samples

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Introduction

• Sample
• My way of experiencing DSLs
• Focus on language oriented DSLs

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Introduction / 2

• Why do we need DSLs?

5
Definitions

• DSL
• A computer programming language of limited
  expressiveness focused on a particular domain

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Definition / 2

• computer programming language
• language nature
• limited expressiveness
• domain focus

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Styles of DSLs

• Internal
• External
• Language Workbenches

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(No Transcript)
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Language Workbench
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Sample

• Input File
• 1234567890123456789012345678901234567890123456789
  01234567890
• SVCLFOWLER 10101MS0120050313..............
  ...........
• SVCLHOHPE 10201DX0320050315..............
  ..........
• SVCLTWO x10301MRP220050329..............
  .............
• USGE10301TWO x50214..7050329.............
  ..........

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DSL 1

• lt?xml version"1.0" encoding"utf-8" ?gt
• ltReaderConfigurationgt
• ltMapping Code "SVCL" TargetClass
  "dsl.ServiceCall"gt
• ltField name "CustomerName" start "4" end
  "18"/gt
• ltField name "CustomerID" start "19" end
  "23"/gt
• ltField name "CallTypeCode" start "24" end
  "27"/gt
• ltField name "DateOfCallString" start "28"
  end "35"/gt
• lt/Mappinggt
• ltMapping Code "USGE" TargetClass
  "dsl.Usage"gt
• ltField name "CustomerID" start "4" end
  "8"/gt
• ltField name "CustomerName" start "9" end
  "22"/gt
• ltField name "Cycle" start "30" end
  "30"/gt
• ltField name "ReadDate" start "31" end
  "36"/gt
• lt/Mappinggt
• lt/ReaderConfigurationgt

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Syntax

• Abstract Syntax - concrete syntax

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DSL 2

• mapping SVCL dsl.ServiceCall
• 4-18 CustomerName
• 19-23 CustomerID
• 24-27 CallTypeCode
• 28-35 DateOfCallString
• mapping USGE dsl.Usage
• 4-8 CustomerID
• 9-22 CustomerName
• 30-30 Cycle
• 31-36 ReadDate

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DSL 3

• mapping('SVCL', ServiceCall) do
• extract 4..18, 'customer_name'
• extract 19..23, 'customer_ID'
• extract 24..27, 'call_type_code'
• extract 28..35, 'date_of_call_string'
• end
• mapping('USGE', Usage) do
• extract 9..22, 'customer_name'
• extract 4..8, 'customer_ID'
• extract 30..30, 'cycle'
• extract 31..36, 'read_date'
• end

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Brownie Example

• take(MicrowaveableDish) do
• melt((1/4).cup.butter)
• mix with gt 6.tablespoon.cocoa
• add 1.cup.sugar, 2.egg, (1/2).teaspoon.vanilla,
  (1/3).cup.flour, (1/4).teaspoon.salt
• mix
• bake in gt BakingPan, for gt 40.minutes, at
  gt 325.degrees
• end

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RSpec

• Demo

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Pro/Cons
Evolving into Generality!
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Different DSLs

• Why do we need DSLs?
• Represent easily businessrules in code

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Different kinds of DSL

• Video

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Domain Experts

• Read and understand
• Not necessarly write!