domain specific languages: the functional way

Domain Specific Languages

The functional Way

Tomas Petricek@tomaspetricek | www.fsharpworks.com

F# Software Foundation

http://www.fsharp.org

software stacks

trainings teaching F# user groups snippets

mac and linux community books and tutorials

consulting open-source MonoDevelop

contributions research support

cross-platform mailing lists

Kaggle• Interactivity• Machine learning• Data processing

GameSys• Time to Market• Social Gaming• Concurrency

Tachyus• Analysis &

reporting• Time to market• Oil & gas startup

Credit Suisse• Complexity• Financial models• DSLs

DSL = model + syntax

COMPOSING 3D OBJECTS

Domain-specific language approach

Class of problemsConstructing 3D objectsMakefiles, stock price modelling, testing, …

Domain-specific language in F#Primitives – basic building blocksComposition – how to put them together

http://tomasp.net/blog/2014/puzzling-fsharp/

GENERATING TEXT DOCUMENTS

Domain model & Processing

What is a text document? How can we process it?

BUILDING AN F# DSL

Operations on documents

Parse Read from Markdown format

Format Generate HTML output

Process Translate to Norwegian!

PROCESSING DOCUMENTS

DSL for writing documents

Creating DSLs with F#=====================

Key components of a DSL:

* **Model** describes the structure of the domain that we are modelling

* **Syntax** provides an easy way for solving problems using the DSL

Creating DSLs with F#

Key components of a DSL:

• Model describes the structure

of the domain that we are modelling

• Syntax provides an easy way for solving problems using the DSL

PARSING MARKDOWN

http://manning.com/petricek2

Processing Markdown

Domain modelUnderstand the problem domain!Using F# discriminated unions

Domain-specific languageInternal – just an F# library!External – parsing Markdown is easy!

DETECTING PRICE PATTERNS

Declining pattern

Rounding top pattern

Multiple bottom pattern

Functional DSL style

Primitive classifiersDeclining priceRising price

Composing classifiersSequence and parallel patternsLinear regression

DETECTING PRICE PATTERNS

Summary

❶ Understand problem domain Primitives & Combinators

❷ Model the language using Discriminated Unions

❸ Add convenient Syntax Internal or External

tomas@tomasp.net | @tomaspetricek | http://fsharpworks.com