/wp-content/plugins/woocommerce/includes/libraries/class-lessc.php

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<?php

/**
 * lessphp v0.4.0
 * http://leafo.net/lessphp
 *
 * LESS CSS compiler, adapted from http://lesscss.org
 *
 * Copyright 2013, Leaf Corcoran <leafot@gmail.com>
 * Licensed under MIT or GPLv3, see LICENSE
 */


/**
 * The LESS compiler and parser.
 *
 * Converting LESS to CSS is a three stage process. The incoming file is parsed
 * by `lessc_parser` into a syntax tree, then it is compiled into another tree
 * representing the CSS structure by `lessc`. The CSS tree is fed into a
 * formatter, like `lessc_formatter` which then outputs CSS as a string.
 *
 * During the first compile, all values are *reduced*, which means that their
 * types are brought to the lowest form before being dump as strings. This
 * handles math equations, variable dereferences, and the like.
 *
 * The `parse` function of `lessc` is the entry point.
 *
 * In summary:
 *
 * The `lessc` class creates an instance of the parser, feeds it LESS code,
 * then transforms the resulting tree to a CSS tree. This class also holds the
 * evaluation context, such as all available mixins and variables at any given
 * time.
 *
 * The `lessc_parser` class is only concerned with parsing its input.
 *
 * The `lessc_formatter` takes a CSS tree, and dumps it to a formatted string,
 * handling things like indentation.
 */
class lessc {
	static public $VERSION = "v0.4.0";

	static public $TRUE = array("keyword", "true");
	static public $FALSE = array("keyword", "false");

	protected $libFunctions = array();
	protected $registeredVars = array();
	protected $preserveComments = false;

	public $vPrefix = '@'; // prefix of abstract properties
	public $mPrefix = '$'; // prefix of abstract blocks
	public $parentSelector = '&';

	public $importDisabled = false;
	public $importDir = '';

	protected $numberPrecision = null;

	protected $allParsedFiles = array();

	// set to the parser that generated the current line when compiling
	// so we know how to create error messages
	protected $sourceParser = null;
	protected $sourceLoc = null;

	static protected $nextImportId = 0; // uniquely identify imports

	// attempts to find the path of an import url, returns null for css files
	protected function findImport($url) {
		foreach ((array)$this->importDir as $dir) {
			$full = $dir.(substr($dir, -1) != '/' ? '/' : '').$url;
			if ($this->fileExists($file = $full.'.less') || $this->fileExists($file = $full)) {
				return $file;
			}
		}

		return null;
	}

	protected function fileExists($name) {
		return is_file($name);
	}

	static public function compressList($items, $delim) {
		if (!isset($items[1]) && isset($items[0])) return $items[0];
		else return array('list', $delim, $items);
	}

	static public function preg_quote($what) {
		return preg_quote($what, '/');
	}

	protected function tryImport($importPath, $parentBlock, $out) {
		if ($importPath[0] == "function" && $importPath[1] == "url") {
			$importPath = $this->flattenList($importPath[2]);
		}

		$str = $this->coerceString($importPath);
		if ($str === null) return false;

		$url = $this->compileValue($this->lib_e($str));

		// don't import if it ends in css
		if (substr_compare($url, '.css', -4, 4) === 0) return false;

		$realPath = $this->findImport($url);

		if ($realPath === null) return false;

		if ($this->importDisabled) {
			return array(false, "/* import disabled */");
		}

		if (isset($this->allParsedFiles[realpath($realPath)])) {
			return array(false, null);
		}

		$this->addParsedFile($realPath);
		$parser = $this->makeParser($realPath);
		$root = $parser->parse(file_get_contents($realPath));

		// set the parents of all the block props
		foreach ($root->props as $prop) {
			if ($prop[0] == "block") {
				$prop[1]->parent = $parentBlock;
			}
		}

		// copy mixins into scope, set their parents
		// bring blocks from import into current block
		// TODO: need to mark the source parser	these came from this file
		foreach ($root->children as $childName => $child) {
			if (isset($parentBlock->children[$childName])) {
				$parentBlock->children[$childName] = array_merge(
					$parentBlock->children[$childName],
					$child);
			} else {
				$parentBlock->children[$childName] = $child;
			}
		}

		$pi = pathinfo($realPath);
		$dir = $pi["dirname"];

		list($top, $bottom) = $this->sortProps($root->props, true);
		$this->compileImportedProps($top, $parentBlock, $out, $parser, $dir);

		return array(true, $bottom, $parser, $dir);
	}

	protected function compileImportedProps($props, $block, $out, $sourceParser, $importDir) {
		$oldSourceParser = $this->sourceParser;

		$oldImport = $this->importDir;

		// TODO: this is because the importDir api is stupid
		$this->importDir = (array)$this->importDir;
		array_unshift($this->importDir, $importDir);

		foreach ($props as $prop) {
			$this->compileProp($prop, $block, $out);
		}

		$this->importDir = $oldImport;
		$this->sourceParser = $oldSourceParser;
	}

	/**
	 * Recursively compiles a block.
	 *
	 * A block is analogous to a CSS block in most cases. A single LESS document
	 * is encapsulated in a block when parsed, but it does not have parent tags
	 * so all of it's children appear on the root level when compiled.
	 *
	 * Blocks are made up of props and children.
	 *
	 * Props are property instructions, array tuples which describe an action
	 * to be taken, eg. write a property, set a variable, mixin a block.
	 *
	 * The children of a block are just all the blocks that are defined within.
	 * This is used to look up mixins when performing a mixin.
	 *
	 * Compiling the block involves pushing a fresh environment on the stack,
	 * and iterating through the props, compiling each one.
	 *
	 * See lessc::compileProp()
	 *
	 */
	protected function compileBlock($block) {
		switch ($block->type) {
		case "root":
			$this->compileRoot($block);
			break;
		case null:
			$this->compileCSSBlock($block);
			break;
		case "media":
			$this->compileMedia($block);
			break;
		case "directive":
			$name = "@" . $block->name;
			if (!empty($block->value)) {
				$name .= " " . $this->compileValue($this->reduce($block->value));
			}

			$this->compileNestedBlock($block, array($name));
			break;
		default:
			$this->throwError("unknown block type: $block->type\n");
		}
	}

	protected function compileCSSBlock($block) {
		$env = $this->pushEnv();

		$selectors = $this->compileSelectors($block->tags);
		$env->selectors = $this->multiplySelectors($selectors);
		$out = $this->makeOutputBlock(null, $env->selectors);

		$this->scope->children[] = $out;
		$this->compileProps($block, $out);

		$block->scope = $env; // mixins carry scope with them!
		$this->popEnv();
	}

	protected function compileMedia($media) {
		$env = $this->pushEnv($media);
		$parentScope = $this->mediaParent($this->scope);

		$query = $this->compileMediaQuery($this->multiplyMedia($env));

		$this->scope = $this->makeOutputBlock($media->type, array($query));
		$parentScope->children[] = $this->scope;

		$this->compileProps($media, $this->scope);

		if (count($this->scope->lines) > 0) {
			$orphanSelelectors = $this->findClosestSelectors();
			if (!is_null($orphanSelelectors)) {
				$orphan = $this->makeOutputBlock(null, $orphanSelelectors);
				$orphan->lines = $this->scope->lines;
				array_unshift($this->scope->children, $orphan);
				$this->scope->lines = array();
			}
		}

		$this->scope = $this->scope->parent;
		$this->popEnv();
	}

	protected function mediaParent($scope) {
		while (!empty($scope->parent)) {
			if (!empty($scope->type) && $scope->type != "media") {
				break;
			}
			$scope = $scope->parent;
		}

		return $scope;
	}

	protected function compileNestedBlock($block, $selectors) {
		$this->pushEnv($block);
		$this->scope = $this->makeOutputBlock($block->type, $selectors);
		$this->scope->parent->children[] = $this->scope;

		$this->compileProps($block, $this->scope);

		$this->scope = $this->scope->parent;
		$this->popEnv();
	}

	protected function compileRoot($root) {
		$this->pushEnv();
		$this->scope = $this->makeOutputBlock($root->type);
		$this->compileProps($root, $this->scope);
		$this->popEnv();
	}

	protected function compileProps($block, $out) {
		foreach ($this->sortProps($block->props) as $prop) {
			$this->compileProp($prop, $block, $out);
		}
		$out->lines = $this->deduplicate($out->lines);
	}

	/**
	 * Deduplicate lines in a block. Comments are not deduplicated. If a
	 * duplicate rule is detected, the comments immediately preceding each
	 * occurence are consolidated.
	 */
	protected function deduplicate($lines) {
		$unique = array();
		$comments = array();

		foreach($lines as $line) {
			if (strpos($line, '/*') === 0) {
				$comments[] = $line;
				continue;
			}
			if (!in_array($line, $unique)) {
				$unique[] = $line;
			}
			array_splice($unique, array_search($line, $unique), 0, $comments);
			$comments = array();
		}
		return array_merge($unique, $comments);
	}

	protected function sortProps($props, $split = false) {
		$vars = array();
		$imports = array();
		$other = array();
		$stack = array();

		foreach ($props as $prop) {
			switch ($prop[0]) {
			case "comment":
				$stack[] = $prop;
				break;
			case "assign":
				$stack[] = $prop;
				if (isset($prop[1][0]) && $prop[1][0] == $this->vPrefix) {
					$vars = array_merge($vars, $stack);
				} else {
					$other = array_merge($other, $stack);
				}
				$stack = array();
				break;
			case "import":
				$id = self::$nextImportId++;
				$prop[] = $id;
				$stack[] = $prop;
				$imports = array_merge($imports, $stack);
				$other[] = array("import_mixin", $id);
				$stack = array();
				break;
			default:
				$stack[] = $prop;
				$other = array_merge($other, $stack);
				$stack = array();
				break;
			}
		}
		$other = array_merge($other, $stack);

		if ($split) {
			return array(array_merge($vars, $imports), $other);
		} else {
			return array_merge($vars, $imports, $other);
		}
	}

	protected function compileMediaQuery($queries) {
		$compiledQueries = array();
		foreach ($queries as $query) {
			$parts = array();
			foreach ($query as $q) {
				switch ($q[0]) {
				case "mediaType":
					$parts[] = implode(" ", array_slice($q, 1));
					break;
				case "mediaExp":
					if (isset($q[2])) {
						$parts[] = "($q[1]: " .
							$this->compileValue($this->reduce($q[2])) . ")";
					} else {
						$parts[] = "($q[1])";
					}
					break;
				case "variable":
					$parts[] = $this->compileValue($this->reduce($q));
				break;
				}
			}

			if (count($parts) > 0) {
				$compiledQueries[] =  implode(" and ", $parts);
			}
		}

		$out = "@media";
		if (!empty($parts)) {
			$out .= " " .
				implode($this->formatter->selectorSeparator, $compiledQueries);
		}
		return $out;
	}

	protected function multiplyMedia($env, $childQueries = null) {
		if (is_null($env) ||
			!empty($env->block->type) && $env->block->type != "media")
		{
			return $childQueries;
		}

		// plain old block, skip
		if (empty($env->block->type)) {
			return $this->multiplyMedia($env->parent, $childQueries);
		}

		$out = array();
		$queries = $env->block->queries;
		if (is_null($childQueries)) {
			$out = $queries;
		} else {
			foreach ($queries as $parent) {
				foreach ($childQueries as $child) {
					$out[] = array_merge($parent, $child);
				}
			}
		}

		return $this->multiplyMedia($env->parent, $out);
	}

	protected function expandParentSelectors(&$tag, $replace) {
		$parts = explode("$&$", $tag);
		$count = 0;
		foreach ($parts as &$part) {
			$part = str_replace($this->parentSelector, $replace, $part, $c);
			$count += $c;
		}
		$tag = implode($this->parentSelector, $parts);
		return $count;
	}

	protected function findClosestSelectors() {
		$env = $this->env;
		$selectors = null;
		while ($env !== null) {
			if (isset($env->selectors)) {
				$selectors = $env->selectors;
				break;
			}
			$env = $env->parent;
		}

		return $selectors;
	}


	// multiply $selectors against the nearest selectors in env
	protected function multiplySelectors($selectors) {
		// find parent selectors

		$parentSelectors = $this->findClosestSelectors();
		if (is_null($parentSelectors)) {
			// kill parent reference in top level selector
			foreach ($selectors as &$s) {
				$this->expandParentSelectors($s, "");
			}

			return $selectors;
		}

		$out = array();
		foreach ($parentSelectors as $parent) {
			foreach ($selectors as $child) {
				$count = $this->expandParentSelectors($child, $parent);

				// don't prepend the parent tag if & was used
				if ($count > 0) {
					$out[] = trim($child);
				} else {
					$out[] = trim($parent . ' ' . $child);
				}
			}
		}

		return $out;
	}

	// reduces selector expressions
	protected function compileSelectors($selectors) {
		$out = array();

		foreach ($selectors as $s) {
			if (is_array($s)) {
				list(, $value) = $s;
				$out[] = trim($this->compileValue($this->reduce($value)));
			} else {
				$out[] = $s;
			}
		}

		return $out;
	}

	protected function eq($left, $right) {
		return $left == $right;
	}

	protected function patternMatch($block, $orderedArgs, $keywordArgs) {
		// match the guards if it has them
		// any one of the groups must have all its guards pass for a match
		if (!empty($block->guards)) {
			$groupPassed = false;
			foreach ($block->guards as $guardGroup) {
				foreach ($guardGroup as $guard) {
					$this->pushEnv();
					$this->zipSetArgs($block->args, $orderedArgs, $keywordArgs);

					$negate = false;
					if ($guard[0] == "negate") {
						$guard = $guard[1];
						$negate = true;
					}

					$passed = $this->reduce($guard) == self::$TRUE;
					if ($negate) $passed = !$passed;

					$this->popEnv();

					if ($passed) {
						$groupPassed = true;
					} else {
						$groupPassed = false;
						break;
					}
				}

				if ($groupPassed) break;
			}

			if (!$groupPassed) {
				return false;
			}
		}

		if (empty($block->args)) {
			return $block->isVararg || empty($orderedArgs) && empty($keywordArgs);
		}

		$remainingArgs = $block->args;
		if ($keywordArgs) {
			$remainingArgs = array();
			foreach ($block->args as $arg) {
				if ($arg[0] == "arg" && isset($keywordArgs[$arg[1]])) {
					continue;
				}

				$remainingArgs[] = $arg;
			}
		}

		$i = -1; // no args
		// try to match by arity or by argument literal
		foreach ($remainingArgs as $i => $arg) {
			switch ($arg[0]) {
			case "lit":
				if (empty($orderedArgs[$i]) || !$this->eq($arg[1], $orderedArgs[$i])) {
					return false;
				}
				break;
			case "arg":
				// no arg and no default value
				if (!isset($orderedArgs[$i]) && !isset($arg[2])) {
					return false;
				}
				break;
			case "rest":
				$i--; // rest can be empty
				break 2;
			}
		}

		if ($block->isVararg) {
			return true; // not having enough is handled above
		} else {
			$numMatched = $i + 1;
			// greater than becuase default values always match
			return $numMatched >= count($orderedArgs);
		}
	}

	protected function patternMatchAll($blocks, $orderedArgs, $keywordArgs, $skip=array()) {
		$matches = null;
		foreach ($blocks as $block) {
			// skip seen blocks that don't have arguments
			if (isset($skip[$block->id]) && !isset($block->args)) {
				continue;
			}

			if ($this->patternMatch($block, $orderedArgs, $keywordArgs)) {
				$matches[] = $block;
			}
		}

		return $matches;
	}

	// attempt to find blocks matched by path and args
	protected function findBlocks($searchIn, $path, $orderedArgs, $keywordArgs, $seen=array()) {
		if ($searchIn == null) return null;
		if (isset($seen[$searchIn->id])) return null;
		$seen[$searchIn->id] = true;

		$name = $path[0];

		if (isset($searchIn->children[$name])) {
			$blocks = $searchIn->children[$name];
			if (count($path) == 1) {
				$matches = $this->patternMatchAll($blocks, $orderedArgs, $keywordArgs, $seen);
				if (!empty($matches)) {
					// This will return all blocks that match in the closest
					// scope that has any matching block, like lessjs
					return $matches;
				}
			} else {
				$matches = array();
				foreach ($blocks as $subBlock) {
					$subMatches = $this->findBlocks($subBlock,
						array_slice($path, 1), $orderedArgs, $keywordArgs, $seen);

					if (!is_null($subMatches)) {
						foreach ($subMatches as $sm) {
							$matches[] = $sm;
						}
					}
				}

				return count($matches) > 0 ? $matches : null;
			}
		}
		if ($searchIn->parent === $searchIn) return null;
		return $this->findBlocks($searchIn->parent, $path, $orderedArgs, $keywordArgs, $seen);
	}

	// sets all argument names in $args to either the default value
	// or the one passed in through $values
	protected function zipSetArgs($args, $orderedValues, $keywordValues) {
		$assignedValues = array();

		$i = 0;
		foreach ($args as  $a) {
			if ($a[0] == "arg") {
				if (isset($keywordValues[$a[1]])) {
					// has keyword arg
					$value = $keywordValues[$a[1]];
				} elseif (isset($orderedValues[$i])) {
					// has ordered arg
					$value = $orderedValues[$i];
					$i++;
				} elseif (isset($a[2])) {
					// has default value
					$value = $a[2];
				} else {
					$this->throwError("Failed to assign arg " . $a[1]);
					$value = null; // :(
				}

				$value = $this->reduce($value);
				$this->set($a[1], $value);
				$assignedValues[] = $value;
			} else {
				// a lit
				$i++;
			}
		}

		// check for a rest
		$last = end($args);
		if ($last[0] == "rest") {
			$rest = array_slice($orderedValues, count($args) - 1);
			$this->set($last[1], $this->reduce(array("list", " ", $rest)));
		}

		// wow is this the only true use of PHP's + operator for arrays?
		$this->env->arguments = $assignedValues + $orderedValues;
	}

	// compile a prop and update $lines or $blocks appropriately
	protected function compileProp($prop, $block, $out) {
		// set error position context
		$this->sourceLoc = isset($prop[-1]) ? $prop[-1] : -1;

		switch ($prop[0]) {
		case 'assign':
			list(, $name, $value) = $prop;
			if ($name[0] == $this->vPrefix) {
				$this->set($name, $value);
			} else {
				$out->lines[] = $this->formatter->property($name,
						$this->compileValue($this->reduce($value)));
			}
			break;
		case 'block':
			list(, $child) = $prop;
			$this->compileBlock($child);
			break;
		case 'mixin':
			list(, $path, $args, $suffix) = $prop;

			$orderedArgs = array();
			$keywordArgs = array();
			foreach ((array)$args as $arg) {
				$argval = null;
				switch ($arg[0]) {
				case "arg":
					if (!isset($arg[2])) {
						$orderedArgs[] = $this->reduce(array("variable", $arg[1]));
					} else {
						$keywordArgs[$arg[1]] = $this->reduce($arg[2]);
					}
					break;

				case "lit":
					$orderedArgs[] = $this->reduce($arg[1]);
					break;
				default:
					$this->throwError("Unknown arg type: " . $arg[0]);
				}
			}

			$mixins = $this->findBlocks($block, $path, $orderedArgs, $keywordArgs);

			if ($mixins === null) {
				$this->throwError("{$prop[1][0]} is undefined");
			}

			foreach ($mixins as $mixin) {
				if ($mixin === $block && !$orderedArgs) {
					continue;
				}

				$haveScope = false;
				if (isset($mixin->parent->scope)) {
					$haveScope = true;
					$mixinParentEnv = $this->pushEnv();
					$mixinParentEnv->storeParent = $mixin->parent->scope;
				}

				$haveArgs = false;
				if (isset($mixin->args)) {
					$haveArgs = true;
					$this->pushEnv();
					$this->zipSetArgs($mixin->args, $orderedArgs, $keywordArgs);
				}

				$oldParent = $mixin->parent;
				if ($mixin != $block) $mixin->parent = $block;

				foreach ($this->sortProps($mixin->props) as $subProp) {
					if ($suffix !== null &&
						$subProp[0] == "assign" &&
						is_string($subProp[1]) &&
						$subProp[1]{0} != $this->vPrefix)
					{
						$subProp[2] = array(
							'list', ' ',
							array($subProp[2], array('keyword', $suffix))
						);
					}

					$this->compileProp($subProp, $mixin, $out);
				}

				$mixin->parent = $oldParent;

				if ($haveArgs) $this->popEnv();
				if ($haveScope) $this->popEnv();
			}

			break;
		case 'raw':
			$out->lines[] = $prop[1];
			break;
		case "directive":
			list(, $name, $value) = $prop;
			$out->lines[] = "@$name " . $this->compileValue($this->reduce($value)).';';
			break;
		case "comment":
			$out->lines[] = $prop[1];
			break;
		case "import";
			list(, $importPath, $importId) = $prop;
			$importPath = $this->reduce($importPath);

			if (!isset($this->env->imports)) {
				$this->env->imports = array();
			}

			$result = $this->tryImport($importPath, $block, $out);

			$this->env->imports[$importId] = $result === false ?
				array(false, "@import " . $this->compileValue($importPath).";") :
				$result;

			break;
		case "import_mixin":
			list(,$importId) = $prop;
			$import = $this->env->imports[$importId];
			if ($import[0] === false) {
				if (isset($import[1])) {
					$out->lines[] = $import[1];
				}
			} else {
				list(, $bottom, $parser, $importDir) = $import;
				$this->compileImportedProps($bottom, $block, $out, $parser, $importDir);
			}

			break;
		default:
			$this->throwError("unknown op: {$prop[0]}\n");
		}
	}


	/**
	 * Compiles a primitive value into a CSS property value.
	 *
	 * Values in lessphp are typed by being wrapped in arrays, their format is
	 * typically:
	 *
	 *     array(type, contents [, additional_contents]*)
	 *
	 * The input is expected to be reduced. This function will not work on
	 * things like expressions and variables.
	 */
	protected function compileValue($value) {
		switch ($value[0]) {
		case 'list':
			// [1] - delimiter
			// [2] - array of values
			return implode($value[1], array_map(array($this, 'compileValue'), $value[2]));
		case 'raw_color':
			if (!empty($this->formatter->compressColors)) {
				return $this->compileValue($this->coerceColor($value));
			}
			return $value[1];
		case 'keyword':
			// [1] - the keyword
			return $value[1];
		case 'number':
			list(, $num, $unit) = $value;
			// [1] - the number
			// [2] - the unit
			if ($this->numberPrecision !== null) {
				$num = round($num, $this->numberPrecision);
			}
			return $num . $unit;
		case 'string':
			// [1] - contents of string (includes quotes)
			list(, $delim, $content) = $value;
			foreach ($content as &$part) {
				if (is_array($part)) {
					$part = $this->compileValue($part);
				}
			}
			return $delim . implode($content) . $delim;
		case 'color':
			// [1] - red component (either number or a %)
			// [2] - green component
			// [3] - blue component
			// [4] - optional alpha component
			list(, $r, $g, $b) = $value;
			$r = round($r);
			$g = round($g);
			$b = round($b);

			if (count($value) == 5 && $value[4] != 1) { // rgba
				return 'rgba('.$r.','.$g.','.$b.','.$value[4].')';
			}

			$h = sprintf("#%02x%02x%02x", $r, $g, $b);

			if (!empty($this->formatter->compressColors)) {
				// Converting hex color to short notation (e.g. #003399 to #039)
				if ($h[1] === $h[2] && $h[3] === $h[4] && $h[5] === $h[6]) {
					$h = '#' . $h[1] . $h[3] . $h[5];
				}
			}

			return $h;

		case 'function':
			list(, $name, $args) = $value;
			return $name.'('.$this->compileValue($args).')';
		default: // assumed to be unit
			$this->throwError("unknown value type: $value[0]");
		}
	}

	protected function lib_pow($args) {
		list($base, $exp) = $this->assertArgs($args, 2, "pow");
		return pow($this->assertNumber($base), $this->assertNumber($exp));
	}

	protected function lib_pi() {
		return pi();
	}

	protected function lib_mod($args) {
		list($a, $b) = $this->assertArgs($args, 2, "mod");
		return $this->assertNumber($a) % $this->assertNumber($b);
	}

	protected function lib_tan($num) {
		return tan($this->assertNumber($num));
	}

	protected function lib_sin($num) {
		return sin($this->assertNumber($num));
	}

	protected function lib_cos($num) {
		return cos($this->assertNumber($num));
	}

	protected function lib_atan($num) {
		$num = atan($this->assertNumber($num));
		return array("number", $num, "rad");
	}

	protected function lib_asin($num) {
		$num = asin($this->assertNumber($num));
		return array("number", $num, "rad");
	}

	protected function lib_acos($num) {
		$num = acos($this->assertNumber($num));
		return array("number", $num, "rad");
	}

	protected function lib_sqrt($num) {
		return sqrt($this->assertNumber($num));
	}

	protected function lib_extract($value) {
		list($list, $idx) = $this->assertArgs($value, 2, "extract");
		$idx = $this->assertNumber($idx);
		// 1 indexed
		if ($list[0] == "list" && isset($list[2][$idx - 1])) {
			return $list[2][$idx - 1];
		}
	}

	protected function lib_isnumber($value) {
		return $this->toBool($value[0] == "number");
	}

	protected function lib_isstring($value) {
		return $this->toBool($value[0] == "string");
	}

	protected function lib_iscolor($value) {
		return $this->toBool($this->coerceColor($value));
	}

	protected function lib_iskeyword($value) {
		return $this->toBool($value[0] == "keyword");
	}

	protected function lib_ispixel($value) {
		return $this->toBool($value[0] == "number" && $value[2] == "px");
	}

	protected function lib_ispercentage($value) {
		return $this->toBool($value[0] == "number" && $value[2] == "%");
	}

	protected function lib_isem($value) {
		return $this->toBool($value[0] == "number" && $value[2] == "em");
	}

	protected function lib_isrem($value) {
		return $this->toBool($value[0] == "number" && $value[2] == "rem");
	}

	protected function lib_rgbahex($color) {
		$color = $this->coerceColor($color);
		if (is_null($color))
			$this->throwError("color expected for rgbahex");

		return sprintf("#%02x%02x%02x%02x",
			isset($color[4]) ? $color[4]*255 : 255,
			$color[1],$color[2], $color[3]);
	}

	protected function lib_argb($color){
		return $this->lib_rgbahex($color);
	}

	/**
	 * Given an url, decide whether to output a regular link or the base64-encoded contents of the file
	 *
	 * @param  array  $value either an argument list (two strings) or a single string
	 * @return string        formatted url(), either as a link or base64-encoded
	 */
	protected function lib_data_uri($value) {
		$mime = ($value[0] === 'list') ? $value[2][0][2] : null;
		$url = ($value[0] === 'list') ? $value[2][1][2][0] : $value[2][0];

		$fullpath = $this->findImport($url);

		if($fullpath && ($fsize = filesize($fullpath)) !== false) {
			// IE8 can't handle data uris larger than 32KB
			if($fsize/1024 < 32) {
				if(is_null($mime)) {
					if(class_exists('finfo')) { // php 5.3+
						$finfo = new finfo(FILEINFO_MIME);
						$mime = explode('; ', $finfo->file($fullpath));
						$mime = $mime[0];
					} elseif(function_exists('mime_content_type')) { // PHP 5.2
						$mime = mime_content_type($fullpath);
					}
				}

				if(!is_null($mime)) // fallback if the mime type is still unknown
					$url = sprintf('data:%s;base64,%s', $mime, base64_encode(file_get_contents($fullpath)));
			}
		}

		return 'url("'.$url.'")';
	}

	// utility func to unquote a string
	protected function lib_e($arg) {
		switch ($arg[0]) {
			case "list":
				$items = $arg[2];
				if (isset($items[0])) {
					return $this->lib_e($items[0]);
				}
				$this->throwError("unrecognised input");
			case "string":
				$arg[1] = "";
				return $arg;
			case "keyword":
				return $arg;
			default:
				return array("keyword", $this->compileValue($arg));
		}
	}

	protected function lib__sprintf($args) {
		if ($args[0] != "list") return $args;
		$values = $args[2];
		$string = array_shift($values);
		$template = $this->compileValue($this->lib_e($string));

		$i = 0;
		if (preg_match_all('/%[dsa]/', $template, $m)) {
			foreach ($m[0] as $match) {
				$val = isset($values[$i]) ?
					$this->reduce($values[$i]) : array('keyword', '');

				// lessjs compat, renders fully expanded color, not raw color
				if ($color = $this->coerceColor($val)) {
					$val = $color;
				}

				$i++;
				$rep = $this->compileValue($this->lib_e($val));
				$template = preg_replace('/'.self::preg_quote($match).'/',
					$rep, $template, 1);
			}
		}

		$d = $string[0] == "string" ? $string[1] : '"';
		return array("string", $d, array($template));
	}

	protected function lib_floor($arg) {
		$value = $this->assertNumber($arg);
		return array("number", floor($value), $arg[2]);
	}

	protected function lib_ceil($arg) {
		$value = $this->assertNumber($arg);
		return array("number", ceil($value), $arg[2]);
	}

	protected function lib_round($arg) {
		if($arg[0] != "list") {
			$value = $this->assertNumber($arg);
			return array("number", round($value), $arg[2]);
		} else {
			$value = $this->assertNumber($arg[2][0]);
			$precision = $this->assertNumber($arg[2][1]);
			return array("number", round($value, $precision), $arg[2][0][2]);
		}
	}

	protected function lib_unit($arg) {
		if ($arg[0] == "list") {
			list($number, $newUnit) = $arg[2];
			return array("number", $this->assertNumber($number),
				$this->compileValue($this->lib_e($newUnit)));
		} else {
			return array("number", $this->assertNumber($arg), "");
		}
	}

	/**
	 * Helper function to get arguments for color manipulation functions.
	 * takes a list that contains a color like thing and a percentage
	 */
	public function colorArgs($args) {
		if ($args[0] != 'list' || count($args[2]) < 2) {
			return array(array('color', 0, 0, 0), 0);
		}
		list($color, $delta) = $args[2];
		$color = $this->assertColor($color);
		$delta = floatval($delta[1]);

		return array($color, $delta);
	}

	protected function lib_darken($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);
		$hsl[3] = $this->clamp($hsl[3] - $delta, 100);
		return $this->toRGB($hsl);
	}

	protected function lib_lighten($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);
		$hsl[3] = $this->clamp($hsl[3] + $delta, 100);
		return $this->toRGB($hsl);
	}

	protected function lib_saturate($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);
		$hsl[2] = $this->clamp($hsl[2] + $delta, 100);
		return $this->toRGB($hsl);
	}

	protected function lib_desaturate($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);
		$hsl[2] = $this->clamp($hsl[2] - $delta, 100);
		return $this->toRGB($hsl);
	}

	protected function lib_spin($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);

		$hsl[1] = $hsl[1] + $delta % 360;
		if ($hsl[1] < 0) $hsl[1] += 360;

		return $this->toRGB($hsl);
	}

	protected function lib_fadeout($args) {
		list($color, $delta) = $this->colorArgs($args);
		$color[4] = $this->clamp((isset($color[4]) ? $color[4] : 1) - $delta/100);
		return $color;
	}

	protected function lib_fadein($args) {
		list($color, $delta) = $this->colorArgs($args);
		$color[4] = $this->clamp((isset($color[4]) ? $color[4] : 1) + $delta/100);
		return $color;
	}

	protected function lib_hue($color) {
		$hsl = $this->toHSL($this->assertColor($color));
		return round($hsl[1]);
	}

	protected function lib_saturation($color) {
		$hsl = $this->toHSL($this->assertColor($color));
		return round($hsl[2]);
	}

	protected function lib_lightness($color) {
		$hsl = $this->toHSL($this->assertColor($color));
		return round($hsl[3]);
	}

	// get the alpha of a color
	// defaults to 1 for non-colors or colors without an alpha
	protected function lib_alpha($value) {
		if (!is_null($color = $this->coerceColor($value))) {
			return isset($color[4]) ? $color[4] : 1;
		}
	}

	// set the alpha of the color
	protected function lib_fade($args) {
		list($color, $alpha) = $this->colorArgs($args);
		$color[4] = $this->clamp($alpha / 100.0);
		return $color;
	}

	protected function lib_percentage($arg) {
		$num = $this->assertNumber($arg);
		return array("number", $num*100, "%");
	}

	// mixes two colors by weight
	// mix(@color1, @color2, [@weight: 50%]);
	// http://sass-lang.com/docs/yardoc/Sass/Script/Functions.html#mix-instance_method
	protected function lib_mix($args) {
		if ($args[0] != "list" || count($args[2]) < 2)
			$this->throwError("mix expects (color1, color2, weight)");

		list($first, $second) = $args[2];
		$first = $this->assertColor($first);
		$second = $this->assertColor($second);

		$first_a = $this->lib_alpha($first);
		$second_a = $this->lib_alpha($second);

		if (isset($args[2][2])) {
			$weight = $args[2][2][1] / 100.0;
		} else {
			$weight = 0.5;
		}

		$w = $weight * 2 - 1;
		$a = $first_a - $second_a;

		$w1 = (($w * $a == -1 ? $w : ($w + $a)/(1 + $w * $a)) + 1) / 2.0;
		$w2 = 1.0 - $w1;

		$new = array('color',
			$w1 * $first[1] + $w2 * $second[1],
			$w1 * $first[2] + $w2 * $second[2],
			$w1 * $first[3] + $w2 * $second[3],
		);

		if ($first_a != 1.0 || $second_a != 1.0) {
			$new[] = $first_a * $weight + $second_a * ($weight - 1);
		}

		return $this->fixColor($new);
	}

	protected function lib_contrast($args) {
	    $darkColor  = array('color', 0, 0, 0);
	    $lightColor = array('color', 255, 255, 255);
	    $threshold  = 0.43;

	    if ( $args[0] == 'list' ) {
	        $inputColor = ( isset($args[2][0]) ) ? $this->assertColor($args[2][0])  : $lightColor;
	        $darkColor  = ( isset($args[2][1]) ) ? $this->assertColor($args[2][1])  : $darkColor;
	        $lightColor = ( isset($args[2][2]) ) ? $this->assertColor($args[2][2])  : $lightColor;
	        $threshold  = ( isset($args[2][3]) ) ? $this->assertNumber($args[2][3]) : $threshold;
	    }
	    else {
	        $inputColor  = $this->assertColor($args);
	    }

	    $inputColor = $this->coerceColor($inputColor);
	    $darkColor  = $this->coerceColor($darkColor);
	    $lightColor = $this->coerceColor($lightColor);

	    //Figure out which is actually light and dark!
	    if ( $this->lib_luma($darkColor) > $this->lib_luma($lightColor) ) {
	        $t  = $lightColor;
	        $lightColor = $darkColor;
	        $darkColor  = $t;
	    }

	    $inputColor_alpha = $this->lib_alpha($inputColor);
	    if ( ( $this->lib_luma($inputColor) * $inputColor_alpha) < $threshold) {
	        return $lightColor;
	    }
	    return $darkColor;
	}

	protected function lib_luma($color) {
	    $color = $this->coerceColor($color);
	    return (0.2126 * $color[0] / 255) + (0.7152 * $color[1] / 255) + (0.0722 * $color[2] / 255);
	}


	public function assertColor($value, $error = "expected color value") {
		$color = $this->coerceColor($value);
		if (is_null($color)) $this->throwError($error);
		return $color;
	}

	public function assertNumber($value, $error = "expecting number") {
		if ($value[0] == "number") return $value[1];
		$this->throwError($error);
	}

	public function assertArgs($value, $expectedArgs, $name="") {
		if ($expectedArgs == 1) {
			return $value;
		} else {
			if ($value[0] !== "list" || $value[1] != ",") $this->throwError("expecting list");
			$values = $value[2];
			$numValues = count($values);
			if ($expectedArgs != $numValues) {
				if ($name) {
					$name = $name . ": ";
				}

				$this->throwError("${name}expecting $expectedArgs arguments, got $numValues");
			}

			return $values;
		}
	}

	protected function toHSL($color) {
		if ($color[0] == 'hsl') return $color;

		$r = $color[1] / 255;
		$g = $color[2] / 255;
		$b = $color[3] / 255;

		$min = min($r, $g, $b);
		$max = max($r, $g, $b);

		$L = ($min + $max) / 2;
		if ($min == $max) {
			$S = $H = 0;
		} else {
			if ($L < 0.5)
				$S = ($max - $min)/($max + $min);
			else
				$S = ($max - $min)/(2.0 - $max - $min);

			if ($r == $max) $H = ($g - $b)/($max - $min);
			elseif ($g == $max) $H = 2.0 + ($b - $r)/($max - $min);
			elseif ($b == $max) $H = 4.0 + ($r - $g)/($max - $min);

		}

		$out = array('hsl',
			($H < 0 ? $H + 6 : $H)*60,
			$S*100,
			$L*100,
		);

		if (count($color) > 4) $out[] = $color[4]; // copy alpha
		return $out;
	}

	protected function toRGB_helper($comp, $temp1, $temp2) {
		if ($comp < 0) $comp += 1.0;
		elseif ($comp > 1) $comp -= 1.0;

		if (6 * $comp < 1) return $temp1 + ($temp2 - $temp1) * 6 * $comp;
		if (2 * $comp < 1) return $temp2;
		if (3 * $comp < 2) return $temp1 + ($temp2 - $temp1)*((2/3) - $comp) * 6;

		return $temp1;
	}

	/**
	 * Converts a hsl array into a color value in rgb.
	 * Expects H to be in range of 0 to 360, S and L in 0 to 100
	 */
	protected function toRGB($color) {
		if ($color[0] == 'color') return $color;

		$H = $color[1] / 360;
		$S = $color[2] / 100;
		$L = $color[3] / 100;

		if ($S == 0) {
			$r = $g = $b = $L;
		} else {
			$temp2 = $L < 0.5 ?
				$L*(1.0 + $S) :
				$L + $S - $L * $S;

			$temp1 = 2.0 * $L - $temp2;

			$r = $this->toRGB_helper($H + 1/3, $temp1, $temp2);
			$g = $this->toRGB_helper($H, $temp1, $temp2);
			$b = $this->toRGB_helper($H - 1/3, $temp1, $temp2);
		}

		// $out = array('color', round($r*255), round($g*255), round($b*255));
		$out = array('color', $r*255, $g*255, $b*255);
		if (count($color) > 4) $out[] = $color[4]; // copy alpha
		return $out;
	}

	protected function clamp($v, $max = 1, $min = 0) {
		return min($max, max($min, $v));
	}

	/**
	 * Convert the rgb, rgba, hsl color literals of function type
	 * as returned by the parser into values of color type.
	 */
	protected function funcToColor($func) {
		$fname = $func[1];
		if ($func[2][0] != 'list') return false; // need a list of arguments
		$rawComponents = $func[2][2];

		if ($fname == 'hsl' || $fname == 'hsla') {
			$hsl = array('hsl');
			$i = 0;
			foreach ($rawComponents as $c) {
				$val = $this->reduce($c);
				$val = isset($val[1]) ? floatval($val[1]) : 0;

				if ($i == 0) $clamp = 360;
				elseif ($i < 3) $clamp = 100;
				else $clamp = 1;

				$hsl[] = $this->clamp($val, $clamp);
				$i++;
			}

			while (count($hsl) < 4) $hsl[] = 0;
			return $this->toRGB($hsl);

		} elseif ($fname == 'rgb' || $fname == 'rgba') {
			$components = array();
			$i = 1;
			foreach	($rawComponents as $c) {
				$c = $this->reduce($c);
				if ($i < 4) {
					if ($c[0] == "number" && $c[2] == "%") {
						$components[] = 255 * ($c[1] / 100);
					} else {
						$components[] = floatval($c[1]);
					}
				} elseif ($i == 4) {
					if ($c[0] == "number" && $c[2] == "%") {
						$components[] = 1.0 * ($c[1] / 100);
					} else {
						$components[] = floatval($c[1]);
					}
				} else break;

				$i++;
			}
			while (count($components) < 3) $components[] = 0;
			array_unshift($components, 'color');
			return $this->fixColor($components);
		}

		return false;
	}

	protected function reduce($value, $forExpression = false) {
		switch ($value[0]) {
		case "interpolate":
			$reduced = $this->reduce($value[1]);
			$var = $this->compileValue($reduced);
			$res = $this->reduce(array("variable", $this->vPrefix . $var));

			if ($res[0] == "raw_color") {
				$res = $this->coerceColor($res);
			}

			if (empty($value[2])) $res = $this->lib_e($res);

			return $res;
		case "variable":
			$key = $value[1];
			if (is_array($key)) {
				$key = $this->reduce($key);
				$key = $this->vPrefix . $this->compileValue($this->lib_e($key));
			}

			$seen =& $this->env->seenNames;

			if (!empty($seen[$key])) {
				$this->throwError("infinite loop detected: $key");
			}

			$seen[$key] = true;
			$out = $this->reduce($this->get($key));
			$seen[$key] = false;
			return $out;
		case "list":
			foreach ($value[2] as &$item) {
				$item = $this->reduce($item, $forExpression);
			}
			return $value;
		case "expression":
			return $this->evaluate($value);
		case "string":
			foreach ($value[2] as &$part) {
				if (is_array($part)) {
					$strip = $part[0] == "variable";
					$part = $this->reduce($part);
					if ($strip) $part = $this->lib_e($part);
				}
			}
			return $value;
		case "escape":
			list(,$inner) = $value;
			return $this->lib_e($this->reduce($inner));
		case "function":
			$color = $this->funcToColor($value);
			if ($color) return $color;

			list(, $name, $args) = $value;
			if ($name == "%") $name = "_sprintf";

			$f = isset($this->libFunctions[$name]) ?
				$this->libFunctions[$name] : array($this, 'lib_'.str_replace('-', '_', $name));

			if (is_callable($f)) {
				if ($args[0] == 'list')
					$args = self::compressList($args[2], $args[1]);

				$ret = call_user_func($f, $this->reduce($args, true), $this);

				if (is_null($ret)) {
					return array("string", "", array(
						$name, "(", $args, ")"
					));
				}

				// convert to a typed value if the result is a php primitive
				if (is_numeric($ret)) $ret = array('number', $ret, "");
				elseif (!is_array($ret)) $ret = array('keyword', $ret);

				return $ret;
			}

			// plain function, reduce args
			$value[2] = $this->reduce($value[2]);
			return $value;
		case "unary":
			list(, $op, $exp) = $value;
			$exp = $this->reduce($exp);

			if ($exp[0] == "number") {
				switch ($op) {
				case "+":
					return $exp;
				case "-":
					$exp[1] *= -1;
					return $exp;
				}
			}
			return array("string", "", array($op, $exp));
		}

		if ($forExpression) {
			switch ($value[0]) {
			case "keyword":
				if ($color = $this->coerceColor($value)) {
					return $color;
				}
				break;
			case "raw_color":
				return $this->coerceColor($value);
			}
		}

		return $value;
	}


	// coerce a value for use in color operation
	protected function coerceColor($value) {
		switch($value[0]) {
			case 'color': return $value;
			case 'raw_color':
				$c = array("color", 0, 0, 0);
				$colorStr = substr($value[1], 1);
				$num = hexdec($colorStr);
				$width = strlen($colorStr) == 3 ? 16 : 256;

				for ($i = 3; $i > 0; $i--) { // 3 2 1
					$t = $num % $width;
					$num /= $width;

					$c[$i] = $t * (256/$width) + $t * floor(16/$width);
				}

				return $c;
			case 'keyword':
				$name = $value[1];
				if (isset(self::$cssColors[$name])) {
					$rgba = explode(',', self::$cssColors[$name]);

					if(isset($rgba[3]))
						return array('color', $rgba[0], $rgba[1], $rgba[2], $rgba[3]);

					return array('color', $rgba[0], $rgba[1], $rgba[2]);
				}
				return null;
		}
	}

	// make something string like into a string
	protected function coerceString($value) {
		switch ($value[0]) {
		case "string":
			return $value;
		case "keyword":
			return array("string", "", array($value[1]));
		}
		return null;
	}

	// turn list of length 1 into value type
	protected function flattenList($value) {
		if ($value[0] == "list" && count($value[2]) == 1) {
			return $this->flattenList($value[2][0]);
		}
		return $value;
	}

	public function toBool($a) {
		if ($a) return self::$TRUE;
		else return self::$FALSE;
	}

	// evaluate an expression
	protected function evaluate($exp) {
		list(, $op, $left, $right, $whiteBefore, $whiteAfter) = $exp;

		$left = $this->reduce($left, true);
		$right = $this->reduce($right, true);

		if ($leftColor = $this->coerceColor($left)) {
			$left = $leftColor;
		}

		if ($rightColor = $this->coerceColor($right)) {
			$right = $rightColor;
		}

		$ltype = $left[0];
		$rtype = $right[0];

		// operators that work on all types
		if ($op == "and") {
			return $this->toBool($left == self::$TRUE && $right == self::$TRUE);
		}

		if ($op == "=") {
			return $this->toBool($this->eq($left, $right) );
		}

		if ($op == "+" && !is_null($str = $this->stringConcatenate($left, $right))) {
			return $str;
		}

		// type based operators
		$fname = "op_${ltype}_${rtype}";
		if (is_callable(array($this, $fname))) {
			$out = $this->$fname($op, $left, $right);
			if (!is_null($out)) return $out;
		}

		// make the expression look it did before being parsed
		$paddedOp = $op;
		if ($whiteBefore) $paddedOp = " " . $paddedOp;
		if ($whiteAfter) $paddedOp .= " ";

		return array("string", "", array($left, $paddedOp, $right));
	}

	protected function stringConcatenate($left, $right) {
		if ($strLeft = $this->coerceString($left)) {
			if ($right[0] == "string") {
				$right[1] = "";
			}
			$strLeft[2][] = $right;
			return $strLeft;
		}

		if ($strRight = $this->coerceString($right)) {
			array_unshift($strRight[2], $left);
			return $strRight;
		}
	}


	// make sure a color's components don't go out of bounds
	protected function fixColor($c) {
		foreach (range(1, 3) as $i) {
			if ($c[$i] < 0) $c[$i] = 0;
			if ($c[$i] > 255) $c[$i] = 255;
		}

		return $c;
	}

	protected function op_number_color($op, $lft, $rgt) {
		if ($op == '+' || $op == '*') {
			return $this->op_color_number($op, $rgt, $lft);
		}
	}

	protected function op_color_number($op, $lft, $rgt) {
		if ($rgt[0] == '%') $rgt[1] /= 100;

		return $this->op_color_color($op, $lft,
			array_fill(1, count($lft) - 1, $rgt[1]));
	}

	protected function op_color_color($op, $left, $right) {
		$out = array('color');
		$max = count($left) > count($right) ? count($left) : count($right);
		foreach (range(1, $max - 1) as $i) {
			$lval = isset($left[$i]) ? $left[$i] : 0;
			$rval = isset($right[$i]) ? $right[$i] : 0;
			switch ($op) {
			case '+':
				$out[] = $lval + $rval;
				break;
			case '-':
				$out[] = $lval - $rval;
				break;
			case '*':
				$out[] = $lval * $rval;
				break;
			case '%':
				$out[] = $lval % $rval;
				break;
			case '/':
				if ($rval == 0) $this->throwError("evaluate error: can't divide by zero");
				$out[] = $lval / $rval;
				break;
			default:
				$this->throwError('evaluate error: color op number failed on op '.$op);
			}
		}
		return $this->fixColor($out);
	}

	function lib_red($color){
		$color = $this->coerceColor($color);
		if (is_null($color)) {
			$this->throwError('color expected for red()');
		}

		return $color[1];
	}

	function lib_green($color){
		$color = $this->coerceColor($color);
		if (is_null($color)) {
			$this->throwError('color expected for green()');
		}

		return $color[2];
	}

	function lib_blue($color){
		$color = $this->coerceColor($color);
		if (is_null($color)) {
			$this->throwError('color expected for blue()');
		}

		return $color[3];
	}


	// operator on two numbers
	protected function op_number_number($op, $left, $right) {
		$unit = empty($left[2]) ? $right[2] : $left[2];

		$value = 0;
		switch ($op) {
		case '+':
			$value = $left[1] + $right[1];
			break;
		case '*':
			$value = $left[1] * $right[1];
			break;
		case '-':
			$value = $left[1] - $right[1];
			break;
		case '%':
			$value = $left[1] % $right[1];
			break;
		case '/':
			if ($right[1] == 0) $this->throwError('parse error: divide by zero');
			$value = $left[1] / $right[1];
			break;
		case '<':
			return $this->toBool($left[1] < $right[1]);
		case '>':
			return $this->toBool($left[1] > $right[1]);
		case '>=':
			return $this->toBool($left[1] >= $right[1]);
		case '=<':
			return $this->toBool($left[1] <= $right[1]);
		default:
			$this->throwError('parse error: unknown number operator: '.$op);
		}

		return array("number", $value, $unit);
	}


	/* environment functions */

	protected function makeOutputBlock($type, $selectors = null) {
		$b = new stdclass;
		$b->lines = array();
		$b->children = array();
		$b->selectors = $selectors;
		$b->type = $type;
		$b->parent = $this->scope;
		return $b;
	}

	// the state of execution
	protected function pushEnv($block = null) {
		$e = new stdclass;
		$e->parent = $this->env;
		$e->store = array();
		$e->block = $block;

		$this->env = $e;
		return $e;
	}

	// pop something off the stack
	protected function popEnv() {
		$old = $this->env;
		$this->env = $this->env->parent;
		return $old;
	}

	// set something in the current env
	protected function set($name, $value) {
		$this->env->store[$name] = $value;
	}


	// get the highest occurrence entry for a name
	protected function get($name) {
		$current = $this->env;

		$isArguments = $name == $this->vPrefix . 'arguments';
		while ($current) {
			if ($isArguments && isset($current->arguments)) {
				return array('list', ' ', $current->arguments);
			}

			if (isset($current->store[$name]))
				return $current->store[$name];
			else {
				$current = isset($current->storeParent) ?
					$current->storeParent : $current->parent;
			}
		}

		$this->throwError("variable $name is undefined");
	}

	// inject array of unparsed strings into environment as variables
	protected function injectVariables($args) {
		$this->pushEnv();
		$parser = new lessc_parser($this, __METHOD__);
		foreach ($args as $name => $strValue) {
			if ($name{0} != '@') $name = '@'.$name;
			$parser->count = 0;
			$parser->buffer = (string)$strValue;
			if (!$parser->propertyValue($value)) {
				throw new Exception("failed to parse passed in variable $name: $strValue");
			}

			$this->set($name, $value);
		}
	}

	/**
	 * Initialize any static state, can initialize parser for a file
	 * $opts isn't used yet
	 */
	public function __construct($fname = null) {
		if ($fname !== null) {
			// used for deprecated parse method
			$this->_parseFile = $fname;
		}
	}

	public function compile($string, $name = null) {
		$locale = setlocale(LC_NUMERIC, 0);
		setlocale(LC_NUMERIC, "C");

		$this->parser = $this->makeParser($name);
		$root = $this->parser->parse($string);

		$this->env = null;
		$this->scope = null;

		$this->formatter = $this->newFormatter();

		if (!empty($this->registeredVars)) {
			$this->injectVariables($this->registeredVars);
		}

		$this->sourceParser = $this->parser; // used for error messages
		$this->compileBlock($root);

		ob_start();
		$this->formatter->block($this->scope);
		$out = ob_get_clean();
		setlocale(LC_NUMERIC, $locale);
		return $out;
	}

	public function compileFile($fname, $outFname = null) {
		if (!is_readable($fname)) {
			throw new Exception('load error: failed to find '.$fname);
		}

		$pi = pathinfo($fname);

		$oldImport = $this->importDir;

		$this->importDir = (array)$this->importDir;
		$this->importDir[] = $pi['dirname'].'/';

		$this->addParsedFile($fname);

		$out = $this->compile(file_get_contents($fname), $fname);

		$this->importDir = $oldImport;

		if ($outFname !== null) {
			return file_put_contents($outFname, $out);
		}

		return $out;
	}

	// compile only if changed input has changed or output doesn't exist
	public function checkedCompile($in, $out) {
		if (!is_file($out) || filemtime($in) > filemtime($out)) {
			$this->compileFile($in, $out);
			return true;
		}
		return false;
	}

	/**
	 * Execute lessphp on a .less file or a lessphp cache structure
	 *
	 * The lessphp cache structure contains information about a specific
	 * less file having been parsed. It can be used as a hint for future
	 * calls to determine whether or not a rebuild is required.
	 *
	 * Th…