aGrammarNotationForTreeLanguages.scroll

date 9/10/2017
tags All Scroll ScrollPapers
title Parsers: a language for making languages

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I introduce the core idea of a new language for making languages.
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# Introduction

Creating a great programming language is a multi-step process. One step in that process is to decide on syntax and formally define a language in a parser notation such as BNF. Unfortunately, like the programming languages they describe, these parser notations are complex, brittle and error-prone.

Below I introduce the core idea of a much simpler parser notation for defining 2D Languages.

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# Parsers: A language for building languages

A microlang in Parsers consists of a set of Parser Definitions including a catchall Parser Definition.

A Parser Definition consists of a match rule and optionally another Parsers microlang.

Everything is encoded in the same sytnax (Particles), hence Parsers is written in Parsers.

# Example

A Parsers file for an imagined microlang called Tally, with 2 Parsers `{+, -}` might look like this:

code
 TallyParser
  catchAllParser errorParser
  parsers
   errorParser
   expressionParser extends TallyParser
    words int+
   +Parser extends expressionParser
   -Parser extends expressionParser

A valid program in the Tally microlang defined by the file above:

code
 + 4 5
  - 1 1

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# Conclusion and Future Work

The introduction above is minimal but shows the core idea: a new notation (Particles) can be used to define new languages in a language (Parsers) that itself is defined in Parsers on top of Particles.

We have developed and open-sourced Parsers a compiler-compiler implementing these ideas.
 https://github.com/breck7/scrollsdk/tree/main/langs/parsers Parsers

Future publications and/or open source releases will delve into the additional features found in the compiler-compiler.

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