Masala Parser

Authors

• Didier Plaindoux
• Nicolas Zozol

Origins

• Direct Style Monadic Parser Combinators For The Real World
• Haskell Parsec
• Existing in JS: Jison, Bennu (Kephri)

Use cases (as today)

• Alternative for Lex & yacc
• Extract data from a big text, replace complex regexp
• Validate complete structure with variations
• Note taking with very customized markdown

Keywords: variations and maintainability

Interesting points

• Works in the browser
• Zero dependence
• 400 unit & integration tests
• 100% coverage
• API now stable
• Typescript d.ts (not tested enough)

Quick Examples

Live Demos:

• Floor Notation
• Tikka Masala
• Operation

Explanations

Floor notation

    // N: Number Bundle, C: Chars Bundle
    import {stream, N,C} from 'parser-combinator';
    const document = '|4.6|';
    
    const floorCombinator= C.char('|')
                            .thenRight( N.numberLiteral )    // we had [ '|' , 4.6], we keep 4.6
                            .thenLeft( C.char('|') )   // we had [ 4.6 , '|' ], we keep 4.6
                            .map(x => Math.floor(x)); // we transform selected value in meaningful value
    
    // Parsec needs a stream of characters
    const parsing = floorCombinator.parse(stream.ofString(document));
    
    console.log( parsing.value === 4 );

Definition

in functional programming, a parser combinator is a higher-order function that accepts several parsers as input and returns a new parser as its output.

!image : curry-paste.jpg

The Monoid structure

!image : parsec.png

Core bundles

• Streams
• Class Parser
• CharBundle, NumberBundle, FlowBundle
• Genlex: ParserStream

... Live demo

The Flow Bundle

The flow bundle will mix ingredients together.

• F.try(parser).or(otherParser)
• F.not(parser): Accept anything else
• F.eos: Accepted if the Parser has reached the End Of Stream

Others:

• F.lazy: Makes a lazy evaluation.
  • May be used for Left recursionue

The Chars Bundle

• letter: accept an ascii letter
• letters: accepts many letters and returns a string
• char(x): accept if next input is x
• lowerCase: accept any next lower case inputs
• ...

The Numbers Bundle

• numberLiteral: accept any float number, such as -2.3E+24
• digit: accept any single digit, and return a single char
• digits: accept many digits, and return a string.
• integer: accept any positive or negative integer

Live demo

.. improving parsing

The Standard bundles

Under development

• Json Parser
• Bricks for custom markdown
• 2 paying clients
  • Extractor
  • Markdown (quick notes)

Lotech

• Markdown for those who write a lot
• Business specific plugins and mini-application
• !bang: specific command with autocompletion
• !!bangbang: newbie popup, access to apps (table, ...)

Quizz Example

    !quizz: La renaissance

    !q: Quelle année pour Marignan ?        
    
    ** 1515
    * 1525
    * 1625

    !include: @jeanne/renaissance 

Course Example

... 95% pure markdown

    !image class=right: gutenberg.jpg

    !image size=small right=right: @nicolas/renaissance.jpg        
    !image small right: @nicolas/renaissance.jpg

    !! => 'bang-bang' ; ouvre une boite de dialogue applicative
        tableaux, addons, ...

Task Force

• Mini-app
• Json pur < Lotech < Interface graphique

    !task: ranger le bureau       
    !team name=Bricolo: Réparer des choses faciles
    !captain: Nicolas
    * Magali
    * Your name here

    !team name=Menuiserie: Fermer la cage d'escalier
    !captain: Pascal
    *  Your name here

Gotcha's

• Hard to debug, especially Genlex
• Sometimes locked (optrep().rep())

Questions ?