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base.js
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base.js
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var b = {};
// exact string match
b.lit = function (str) {
return function (from) {
if (this.source.substr(from, str.length) === str)
return {val: str, next: from + str.length};
this.fail(from, JSON.stringify(str));
return null;
};
};
// exact string match (case insensitive)
b.liti = function (str) {
str = str.toLowerCase();
return function (from) {
if (this.source.substr(from, str.length).toLowerCase() === str)
return {val: str, next: from + str.length};
this.fail(from, JSON.stringify(str) + "i");
return null;
};
};
// sequence
b.seq = function (/* args */) {
var args = Array.prototype.slice.call(arguments);
return function (from) {
var curr = from, self = this, ret = [];
return args.every(function (arg) {
var res = arg.bind(self)(curr);
if (res) { ret.push(res.val); curr = res.next; }
return res;
}) && {val: ret, next: curr};
};
};
// alternatives
b.par = function (/* args */) {
var args = Array.prototype.slice.call(arguments);
return function (from) {
var self = this, ret;
return args.some(function (arg) {
var res = arg.bind(self)(from);
if (res) { ret = res.val; from = res.next; }
return res;
}) && {val: ret, next: from};
};
};
// a*
b.any = function (arg) {
return function (from) {
var f = arg.bind(this), res, ret = [];
while (res = f(from))
ret.push(res.val), from = res.next;
return {val: ret, next: from};
};
};
// empty string
b.eps = function (from) {
return {val: null, next: from};
};
// one arbitrary character
b.chr = function (from) {
if (from < this.source.length)
return {val: this.source[from], next: from + 1};
this.fail(from, "any char");
return null;
};
// a+
b.some = function (arg) {
return b.flat(b.seq(arg, b.any(arg)), function (a, c) {
return c.unshift(a), c;
});
};
// a?
b.maybe = function (arg) {
return b.par(arg, b.eps);
};
// mutual recursion of rules
b.ref = function (rule /*, args */) {
var args = Array.prototype.slice.call(arguments);
args.shift();
return function (from) {
return rule.apply(null, args).call(this, from);
};
};
// work with parser's return value
b.apply = function (p, f) {
return function (from) {
var res = p.bind(this)(from);
if (!res) return res;
res.val = f(res.val);
return res;
};
};
// same as `apply`, but array becomes a list of arguments
b.flat = function (p, f) {
return b.apply(p, function (xs) {
return f.apply(null, xs);
});
};
// positive lookahead
b.poscheck = function (parser) {
return function (from) {
var res = parser.bind(this)(from);
return res ? {val: res.val, next: from} : null;
};
};
// positive lookahead
b.negcheck = function (parser) {
return function (from) {
var res = parser.bind(this)(from);
return res ? null : {val: null, next: from};
};
};
// get result as parsed string
b.str = function (p) {
return function (from) {
var ret = p.bind(this)(from);
return ret && {val: this.source.substr(from, ret.next - from), next: ret.next};
};
};
// check if character satisfies criteria
b.satisfy = function (f, message) {
return function (from) {
if (from < this.source.length && f(this.source[from]))
return {val: this.source[from], next: from + 1};
this.fail(from, message);
return null;
};
};
function asc(c) {
return c.charCodeAt(0);
}
function escape(c) {
var str = JSON.stringify(c);
return str.substr(1, str.length - 2);
}
// check for character range
b.range = function (a, d) {
return b.satisfy(function (c) {
return asc(a) <= asc(c) && asc(c) <= asc(d);
}, "[" + escape(a) + "-" + escape(d) + "]");
};
// end of input
b.eof = function (from) {
if (from >= this.source.length)
return {val: null, next: from};
this.fail(from, "end of input");
return null;
};
// {n}
b.exact = function (arg, n) {
return function (from) {
var f = arg.bind(this), ret = [];
for (var i = 0; i < n; ++i) {
var res = f(from);
if (!res) return null;
ret.push(res.val);
from = res.next;
}
return {val: ret, next: from};
};
};
// {n,}
b.atleast = function (arg, n) {
return function (from) {
var f = arg.bind(this), ret = [];
for (var i = 0;; ++i) {
var res = f(from);
if (!res) return i < n ? null : {val: ret, next: from};
ret.push(res.val);
from = res.next;
}
};
};
// (n, m)
b.between = function (arg, n, m) {
return function (from) {
var f = arg.bind(this), ret = [];
for (var i = 0; i < m; ++i) {
var res = f(from);
if (!res) return i < n ? null : {val: ret, next: from};
ret.push(res.val);
from = res.next;
}
return {val: ret, next: from};
};
};
var state_t = function (source) {
this.source = source;
this.last = 0;
this.fails = [];
};
state_t.prototype.fail = function (from, str) {
if (this.last < from)
this.fails = {}, this.last = from;
this.fails[str] = true;
};
// parse given string with given parser
b.parse = function (parser, source) {
var state = new state_t(source);
var ret = parser.bind(state)(0);
if (!ret || ret.next != source.length) {
var fails = [];
for (var fail in state.fails) if (state.fails.hasOwnProperty(fail)) fails.push(fail);
throw "Expected " + fails.join(", ") + " but got " + JSON.stringify(source[state.last]);
}
return ret;
};
module.exports = b;