Nearley - Grammar language

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Nearley is an open source grammar language created in 2014 by Kartik Chandra.

#226on PLDB

10Years Old

53Repos

Download source code:

git clone https://github.com/Hardmath123/nearley

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📜🔜🌲 Simple, fast, powerful parser toolkit for JavaScript.

Tags: grammarLanguage
Nearley is developed on GitHub and has 3,578 stars
There are at least 53 Nearley repos on GitHub
Early development of Nearley happened in https://github.com/kach/nearley/issues
Nearley is written in JavaScript, HTML, Markdown, JSON, SVG, CSS, YAML, Bourne shell
The Google BigQuery Public Dataset GitHub snapshot shows 32 users using Nearley in 33 repos on GitHub
GitHub supports syntax highlighting for Nearley

Example from Linguist:

# nearley grammar
@builtin "string.ne"

@{%

function insensitive(sl) {
    var s = sl.literal;
    result = [];
    for (var i=0; i<s.length; i++) {
        var c = s.charAt(i);
        if (c.toUpperCase() !== c || c.toLowerCase() !== c) {
            result.push(new RegExp("[" + c.toLowerCase() + c.toUpperCase() + "]"));
        } else {
            result.push({literal: c});
        }
    }
    return {subexpression: [{tokens: result, postprocess: function(d) {return d.join(""); }}]};
}

%}

final -> whit? prog whit?  {% function(d) { return d[1]; } %}

prog -> prod  {% function(d) { return [d[0]]; } %}
      | prod whit prog  {% function(d) { return [d[0]].concat(d[2]); } %}

prod -> word whit? ("-"|"="):+ ">" whit? expression+  {% function(d) { return {name: d[0], rules: d[5]}; } %}
      | word "[" wordlist "]" whit? ("-"|"="):+ ">" whit? expression+ {% function(d) {return {macro: d[0], args: d[2], exprs: d[8]}} %}
      | "@" whit? js  {% function(d) { return {body: d[2]}; } %}
      | "@" word whit word  {% function(d) { return {config: d[1], value: d[3]}; } %}
      | "@include"  whit? string {% function(d) {return {include: d[2].literal, builtin: false}} %}
      | "@builtin"  whit? string {% function(d) {return {include: d[2].literal, builtin: true }} %}

expression+ -> completeexpression
             | expression+ whit? "|" whit? completeexpression  {% function(d) { return d[0].concat([d[4]]); } %}

expressionlist -> completeexpression
             | expressionlist whit? "," whit? completeexpression {% function(d) { return d[0].concat([d[4]]); } %}

wordlist -> word
            | wordlist whit? "," whit? word {% function(d) { return d[0].concat([d[4]]); } %}

completeexpression -> expr  {% function(d) { return {tokens: d[0]}; } %}
                    | expr whit? js  {% function(d) { return {tokens: d[0], postprocess: d[2]}; } %}

expr_member ->
      word {% id %}
    | "TEMPLATEquot; word {% function(d) {return {mixin: d[1]}} %}
    | word "[" expressionlist "]" {% function(d) {return {macrocall: d[0], args: d[2]}} %}
    | string "i":? {% function(d) { if (d[1]) {return insensitive(d[0]); } else {return d[0]; } } %}
    | "%" word {% function(d) {return {token: d[1]}} %}
    | charclass {% id %}
    | "(" whit? expression+ whit? ")" {% function(d) {return {'subexpression': d[2]} ;} %}
    | expr_member whit? ebnf_modifier {% function(d) {return {'ebnf': d[0], 'modifier': d[2]}; } %}

ebnf_modifier -> ":+" {% id %} | ":*" {% id %} | ":?" {% id %}

expr -> expr_member
      | expr whit expr_member  {% function(d){ return d[0].concat([d[2]]); } %}

word -> [\w\?\+]  {% function(d){ return d[0]; } %}
      | word [\w\?\+]  {% function(d){ return d[0]+d[1]; } %}

string -> dqstring {% function(d) {return { literal: d[0] }; } %}
#string -> "\"" charset "\""  {% function(d) { return { literal: d[1].join("") }; } %}
#
#charset -> null
#         | charset char  {% function(d) { return d[0].concat([d[1]]); } %}
#
#char -> [^\\"]  {% function(d) { return d[0]; } %}
#      | "\\" .  {% function(d) { return JSON.parse("\""+"\\"+d[1]+"\""); } %}

charclass -> "."  {% function(d) { return new RegExp("."); } %}
           | "[" charclassmembers "]"  {% function(d) { return new RegExp("[" + d[1].join('') + "]"); } %}

charclassmembers -> null
                  | charclassmembers charclassmember  {% function(d) { return d[0].concat([d[1]]); } %}

charclassmember -> [^\\\]]  {% function(d) { return d[0]; } %}
                 | "\\" .  {% function(d) { return d[0] + d[1]; } %}

js -> "{" "%" jscode "%" "}"  {% function(d) { return d[2]; } %}

jscode -> null  {% function() {return "";} %}
        | jscode [^%]  {% function(d) {return d[0] + d[1];} %}
        | jscode "%" [^}] {% function(d) {return d[0] + d[1] + d[2]; } %}

# Whitespace with a comment
whit -> whitraw
      | whitraw? comment whit?

# Optional whitespace with a comment
whit? -> null
       | whit

# Literally a string of whitespace
whitraw -> [\s]
         | whitraw [\s]

# A string of whitespace OR the empty string
whitraw? -> null
          | whitraw

comment -> "#" commentchars "\n"
commentchars -> null
              | commentchars [^\n]

Language features

Feature	Supported	Example	Token
Booleans	✓		true false
Comments	✓	# A comment
Line Comments	✓	# A comment	#
Semantic Indentation	X