S-Expression grammar for PEG.js

sexp-with-__.peg

/*
 * Grammar to generate an S-Expressions parser for Javascript using http://pegjs.majda.cz/
 * Example: (+ 1 2) (car (quote (1 2 "test")))
 * Features: 
 - backslash symbols ("quote\"here"), 
 - one-line comments starts from ";"
 
 - add "__" for identifiers - convert (car (quote (1 2 "three"))) to ["__car",["__quote",[1,2,"three"]]]
 -- to change behavior replace 
 return "__"+identifier.map(function(a) {return concat(a)}).join(""); 
 to 
 return identifier.map(function(a) {return concat(a)}).join("");
 */

start
  = expression*


integer "integer"
  = digits:[0-9]+ { return parseInt(digits.join(""), 10); }


expression
  = (space? '(' body:body ')' space?) { return body; }

body
  = body:(expression / identifier / float / integer / string / space / comment )* { return body.filter(function(a) { return (a != ""); }) }


float
  = ('+' / '-')? [0-9]+ (('.' [0-9]+) / ('e' [0-9]+))


/* ----- 7. Strings with quotation - from JSON parsing ----- */

string "string"
  = quotation_mark chars:char* quotation_mark { return chars.join(""); }

char
  = unescaped
  / escape
    sequence:(
        '"'
      / "\\"
      / "/"
     )
    { return sequence; }

escape         = "\\"
quotation_mark = '"'
unescaped      = [\x20-\x21\x23-\x5B\x5D-\u10FFFF]


identifier
  = identifier:([a-zA-Z\=\*\#:] [a-zA-Z0-9_\=\*-:]*) {
  function concat(o,i){
    var r=[];
    for(var p in o){
        r.push(o[p]);
    }
    return r.join("");
  }
return "__"+identifier.map(function(a) {return concat(a)}).join("");
}

space
  = [\s\n\t ]+ { return ""; }

comment
  = (";" chars:char* [\n\r]) { return ""; }