syntax-diagrams's Introduction

Sequence Diagrams

This library is used to generate syntax diagrams (https://en.wikipedia.org/wiki/Syntax_diagram) from Scala code. Features:

Grammar is defined directly in Scala
Diagrams are generated as SVG files:
- Can be styled via CSS
- Non-terminals can be rendered as links to separate diagrams

Usage

Diagrams are represented by type Expr. You can use its subclasses to construct primitives and combine them into larger expressions:

Symbols
- Terminal(value: String)
- NonTerminal(value: String)
- Special(value: String) - special kind of terminal. For example: textual description, regexp etc.
Combinators
- Repeat(e: Expr) - at least one e
- Optional(e: Expr) - e or nothing
- Choice(es: Seq[Expr]) - selects one of the alternatives
- Sequence(es: Seq[Expr]) - joins es in a sequence (concatenation)

Diagrams are generated by the method SVG.createDiagram:

def createDiagram(rhs: Expr, options: Options = Options()): Tag

You can specify the following options:

maxWidth - maximal width of the diagram. This is not a hard constraint - the generator does its best to fit the diagram but it may fail to do so.
cssClass - css class name used in generated SVG diagram
embeddedStyle - CSS to embed directly in SVG
linker: String => String - method used to convert NonTerminals to HTML links. For example "#" + _. By default does nothing (_ => "").
showNonTerm: String => String - method used to convert NonTerminals to HTML links. For example "#" + _. By default does nothing (_ => "").

Example

See JsonExampleRunner.scala for example that generates a single html page with syntax diagrams for JSON. You can see the generated page here: JSON Syntax

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