gistfile1.js

// BNF parser framework for JavaScript
// Oleg Andreev

  var result = (function(text){
    
    // The Y Combinator
    var Y=function (gen) {
    return function(f) {return f(f)}(
     function(f) {
      return gen(function() {return f(f).apply(null, arguments)})})}
    
    function ToArray(args)
    {
      var arr = []
      for (var i = 0; i < args.length; i++) arr.push(args[i])
      return arr
    }
    
    function Optional(func)
    {
      return function(text, state) {
        return func(text, state) || text
      }
    }
    
    function Char(string)
    {
      return function(text, state) {
        return ((string.indexOf(text.charAt(0)) > -1) ? text.substr(1) : null)
      }
    }
    
    function Any()
    {
      var args = ToArray(arguments)
      return function(text, state) {
        var r = null
        for each (var arg in args)
        {
          r = arg(text, state)
          if (r) return r
        }
        return null
      }
    }
    
    function All()
    {
      var args = ToArray(arguments)
      return function(text, state) {
        for each (var arg in args)
        {
          text = arg(text, state)
          if (!text) return text
        }
        return text
      }
    }
    
    function Capture(func, hook)
    {
      return function(text, state)
      {
        var r = func(text, state)
        if (r) hook(text.substr(0, text.length - r.length), state)
        return r
      }
    }
    
    /*
    sign       := "+" | "-"
    digit      := 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
    integer    := digit integer | digit
    float      := integer "." integer
    unsigned   := float | integer
    signed     := sign optspace unsigned
    number     := signed | unsigned
    */

    var spacechar   = Char(" \t")
    var optspace    = Y(function(os){ return Optional(All(spacechar, os)) })
    var space       = All(spacechar, optspace)
    
    var sign        = Char("+-")
    var digit       = Char("0123456789")
    var integer     = Y(function(i){ return All(digit, Optional(i)) })
    var float       = All(integer, Char("."), integer)
    var unsigned    = Any(float, integer)
    var signed      = All(sign, optspace, unsigned)
    var number      = Capture(Any(signed,unsigned), function(buffer, state) { 
      state.push(buffer)
    })
    
    var numbers     = Y(function(ns){ return All(number, optspace, Optional(ns)) })
    var main        = All(optspace, numbers, optspace)

    var scanner = main
        
    var numbers = []
    var r = scanner(text + " ", numbers) // tail space is intended
    if(!r)
      print("Syntax error!") 
    else
      print("Result is '"+ r +"'")
    
    return numbers
    
  })("  + 1.23  +45 678")