We will see how to build Domain Specific Languages using Kotlin. This approach is an alternative to use existing Language Workbenches such as Jetbrains MPS or Xtext. We reuse existing components such as ANTLR and Kanvas and use them to create with a limited effort complete support for our language including a parser, an editor, a simulator, an interpreter.

1. Building Languages
using Kotlin
Lyon Kotlin User Group - Federico Tomassetti

2. Hi, I am Federico
Once upon I time…
● Got a PhD in Language Engineering
● Done research in Italy & Germany
● Worked at TripAdvisor
● Worked at Groupon
Now I am an independent consultant on
Language Engineering. I design and build:
● Parsers
● Interpreters
● Compilers
● Editors

3. Why building languages?
The language or notation we are
using to express or record our
thoughts, are the major factors
determining what we can think or
express at all!
Edsger W. Dijkstra - The Humble Programmer

4. What pieces do we need
1. Parser
2. Validator
3. Compiler/Interpreter
4. Editor

5. Building languages
is expensive

6. Language Workbenches
Good if:
1) You are ok with the constraints
2) You invest tons of time learning time
3) Dependencies are not an issue

7. Why Kotlin?
Because creating this
stuff is complex
and we need
K-superpowers to
manage doing that!

8. State Machines
Turned off Turned on
Low speed High speed
EmergencyStop
IncreaseSpeed
IncreaseSpeed
LowerSpeed
LowerSpeed
off
on

9. Our example (1/2)
statemachine mySm
input lowSpeedThroughtput: Int
input highSpeedThroughtput: Int
var totalProduction = 0
event turnOff
event turnOn
event speedUp
event speedDown
event emergencyStop
event doNothing

10. Our example (2/2)
start state turnedOff {
on turnOn -> turnedOn
}
state lowSpeed {
on entry {
totalProduction = totalProduction + lowSpeedThroughtput
print("Producing " + lowSpeedThroughtput + " elements (total
"+totalProduction+")")
}
on speedDown -> turnedOn
on speedUp -> highSpeed
on doNothing -> lowSpeed
}
… more states …

11. ModelCode
Validation
Interpreter
Compiler
The process

12. Building a model
1
2
3
Tokens
Parse
Tree
Abstract
Syntax
Tree

13. Tokens
Let’s see the code

14. Want more?
Code: https://github.com/ftomassetti/smlang-example
Book: https://leanpub.com/create_languages
Blog: https://tomassetti.me