diff --git a/.travis.yml b/.travis.yml
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+language: node_js
+node_js:
+  - 0.8
+  - "0.10"
+  - 0.11
diff --git a/README.md b/README.md
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+#nth-check [![Build Status](https://travis-ci.org/fb55/nth-check.png)](https://travis-ci.org/fb55/nth-check)
+
+A performant nth-check parser & compiler.
+
+###About
+
+This module can be used to parse & compile nth-checks, as they are found in CSS 3's `nth-child()` and `nth-last-of-type()`.
+
+`nth-check` focusses on speed, providing optimized functions for different kinds of nth-child formulas, while still following the [spec](http://www.w3.org/TR/css3-selectors/#nth-child-pseudo).
+
+###API
+
+```js
+var nthCheck = require("nth-check");
+```
+
+#####`nthCheck(formula)`
+
+First parses, then compiles the formula.
+
+#####`nthCheck.parse(formula)`
+
+Parses the expression, throws a `SyntaxError` if it fails, otherwise returns an array containing two elements.
+
+__Example:__
+
+```js
+nthCheck.parse("2n+3") //[2, 3]
+```
+
+#####`nthCheck.compile([a, b])`
+
+Takes an array with two elements (as returned by `.parse`) and returns a highly optimized function.
+
+If the formula doesn't match any elements, it returns [`boolbase`](https://github.com/fb55/boolbase)'s `falseFunc`, otherwise, a function accepting an _index_ is returned, which returns whether or not a passed _index_ matches the formula. (Note: The spec starts counting at `1`, the returned function at `0`).
+
+__Example:__
+```js
+var check = nthCheck.compile([2, 3]);
+
+check(0) //false
+check(1) //false
+check(2) //true
+check(3) //false
+check(4) //true
+check(5) //false
+check(6) //true
+```
+
+---
+License: BSD
diff --git a/compile.js b/compile.js
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+++ b/compile.js
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+module.exports = compile;
+
+var BaseFuncs = require("boolbase"),
+    trueFunc  = BaseFuncs.trueFunc,
+    falseFunc = BaseFuncs.falseFunc;
+
+/*
+	returns a function that checks if an elements index matches the given rule
+	highly optimized to return the fastest solution
+*/
+function compile(parsed){
+	var a = parsed[0],
+	    b = parsed[1] - 1;
+
+	//when b <= 0, a*n won't be possible for any matches when a < 0
+	//besides, the specification says that no element is matched when a and b are 0
+	if(b < 0 && a <= 0) return falseFunc;
+
+	//when a is in the range -1..1, it matches any element (so only b is checked)
+	if(a ===-1) return function(pos){ return pos <= b; };
+	if(a === 0) return function(pos){ return pos === b; };
+	//when b <= 0 and a === 1, they match any element
+	if(a === 1) return b < 0 ? trueFunc : function(pos){ return pos >= b; };
+
+	//when a > 0, modulo can be used to check if there is a match
+	var bMod = b % a;
+	if(bMod < 0) bMod += a;
+
+	if(a > 1){
+		return function(pos){
+			return pos >= b && pos % a === bMod;
+		};
+	}
+
+	a *= -1; //make `a` positive
+
+	return function(pos){
+		return pos <= b && pos % a === bMod;
+	};
+}
\ No newline at end of file
diff --git a/index.js b/index.js
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+++ b/index.js
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+var parse = require("./parse.js"),
+    compile = require("./compile.js");
+
+module.exports = function nthCheck(formula){
+	return compile(parse(formula));
+};
+
+module.exports.parse = parse;
+module.exports.compile = compile;
\ No newline at end of file
diff --git a/package.json b/package.json
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+++ b/package.json
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+{
+  "name": "nth-check",
+  "version": "1.0.1",
+  "description": "performant nth-check parser & compiler",
+  "main": "index.js",
+  "scripts": {
+    "test": "node test"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/fb55/nth-check"
+  },
+  "keywords": [
+    "nth-child",
+    "nth",
+    "css"
+  ],
+  "author": "Felix Boehm <me@feedic.com>",
+  "license": "BSD",
+  "bugs": {
+    "url": "https://github.com/fb55/nth-check/issues"
+  },
+  "homepage": "https://github.com/fb55/nth-check",
+  "dependencies": {
+    "boolbase": "~1.0.0"
+  }
+}
diff --git a/parse.js b/parse.js
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+++ b/parse.js
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+module.exports = parse;
+
+//following http://www.w3.org/TR/css3-selectors/#nth-child-pseudo
+
+//[ ['-'|'+']? INTEGER? {N} [ S* ['-'|'+'] S* INTEGER ]?
+var re_nthElement = /^([+\-]?\d*n)?\s*(?:([+\-]?)\s*(\d+))?$/;
+
+/*
+	parses a nth-check formula, returns an array of two numbers
+*/
+function parse(formula){
+	formula = formula.trim().toLowerCase();
+
+	if(formula === "even"){
+		return [2, 0];
+	} else if(formula === "odd"){
+		return [2, 1];
+	} else {
+		var parsed = formula.match(re_nthElement);
+
+		if(!parsed){
+			throw new SyntaxError("n-th rule couldn't be parsed ('" + formula + "')");
+		}
+
+		var a;
+
+		if(parsed[1]){
+			a = parseInt(parsed[1], 10);
+			if(isNaN(a)){
+				if(parsed[1].charAt(0) === "-") a = -1;
+				else a = 1;
+			}
+		} else a = 0;
+
+		return [
+			a,
+			parsed[3] ? parseInt((parsed[2] || "") + parsed[3], 10) : 0
+		];
+	}
+}
diff --git a/test.js b/test.js
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--- /dev/null
+++ b/test.js
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+var nthCheck = require("./"),
+    assert = require("assert");
+
+var invalid = ["-", "asdf", "2n+-0", "2+0", "- 1n", "-1 n"];
+
+function parseInvalid(){
+	invalid.forEach(function(formula){
+		assert.throws(function(){
+				nthCheck.parse(formula);
+			},
+			SyntaxError,
+			formula
+		);
+	});
+}
+
+var valid = {
+	"1": [ 0, 1 ],
+	"2": [ 0, 2 ],
+	"3": [ 0, 3 ],
+	"5": [ 0, 5 ],
+	" 1 ": [ 0, 1 ],
+	" 5 ": [ 0, 5 ],
+	"+2n + 1": [ 2, 1 ],
+	"-1": [ 0, -1 ],
+	"-1n + 3": [ -1, 3 ],
+	"-1n+3": [ -1, 3 ],
+	"-n+2": [ -1, 2 ],
+	"-n+3": [ -1, 3 ],
+	"0n+3": [ 0, 3 ],
+	"1n": [ 1, 0 ],
+	"1n+0": [ 1, 0 ],
+	"2n": [ 2, 0 ],
+	"2n + 1": [ 2, 1 ],
+	"2n+1": [ 2, 1 ],
+	"3n": [ 3, 0 ],
+	"3n+0": [ 3, 0 ],
+	"3n+1": [ 3, 1 ],
+	"3n+2": [ 3, 2 ],
+	"3n+3": [ 3, 3 ],
+	"3n-1": [ 3, -1 ],
+	"3n-2": [ 3, -2 ],
+	"3n-3": [ 3, -3 ],
+	even: [ 2, 0 ],
+	n: [ 1, 0 ],
+	"n+2": [ 1, 2 ],
+	odd: [ 2, 1 ],
+
+	//surprisingly, neither sizzle, qwery or nwmatcher cover these cases
+	"-4n+13": [-4, 13],
+	"-2n + 12": [-2, 12]
+};
+
+function parseValid(){
+	Object.keys(valid).forEach(function(formula){
+		assert.deepEqual(nthCheck.parse(formula), valid[formula], formula);
+	});
+}
+
+function testValid(){
+	Object.keys(valid).forEach(function(formula){
+		testFormula(valid[formula], formula);
+	});
+}
+
+var valArray = Array.apply(null, Array(2e3)).map(function(_, i){return i;});
+
+function testFormula(formula, name){
+	var filtered = valArray.filter(nthCheck.compile(formula)),
+	    iterated = stupidNth(formula);
+
+	try {
+		assert.deepEqual(filtered, iterated, name);
+	} catch(e){
+		e.expected = JSON.stringify(iterated) + " " + name;
+		e.actual = JSON.stringify(filtered) + " " + name;
+		throw e;
+	}
+}
+
+function stupidNth(formula, limit){
+	var a = formula[0],
+	    b = formula[1];
+
+	if(a === 0 && b > 0) return [b - 1];
+
+	//taken from qwery
+	return valArray.filter(function(val){
+		for(var i = b, l = valArray.length; ((a > 0) ? (i <= l) : (i >= 1)); i += a){
+			if(val === valArray[i - 1]) return true;
+		}
+	});
+}
+
+process.stdout.write("- parser");
+process.stdout.write("\n  - parse invalid:\t");
+parseInvalid();
+process.stdout.write("X\n  - parse valid:\t");
+parseValid();
+process.stdout.write("X\n- check values:  \t");
+testValid();
+process.stdout.write("X\n");