Parses SassScript. SassScript is lexed into {@link http://en.wikipedia.org/wiki/Reverse_Polish_notation Reverse Polish notation} by the SassScriptLexer and
the calculated result returned.
/**
* Evaluate a SassScript.
* @param string $expression expression to parse
* @param SassContext $context the context in which the expression is evaluated
* @param integer $environment the environment in which the expression is evaluated
* @return SassLiteral parsed value
*/
public function evaluate($expression, $context, $environment = self::DEFAULT_ENV)
{
self::$context = $context;
$operands = array();
$tokens = $this->parse($expression, $context, $environment);
while (count($tokens)) {
$token = array_shift($tokens);
if ($token instanceof SassScriptFunction) {
$perform = $token->perform();
array_push($operands, $perform);
} elseif ($token instanceof SassLiteral) {
if ($token instanceof SassString) {
$token = new SassString($this->interpolate($token->toString(), self::$context));
}
array_push($operands, $token);
} else {
$args = array();
for ($i = 0, $c = $token->operandCount; $i < $c; $i++) {
$args[] = array_pop($operands);
}
array_push($operands, $token->perform($args));
}
}
return self::makeSingular($operands);
}
public static function colour_stops()
{
$args = func_get_args();
$list = array();
foreach ($args as $arg) {
if ($arg instanceof SassColour) {
$list[] = new CompassColourStop($arg);
} elseif ($arg instanceof SassString) {
# We get a string as the result of concatenation
# So we have to reparse the expression
$colour = $stop = null;
if (empty($parser)) {
$parser = new SassScriptParser();
}
$expr = $parser->parse($arg->value, SassScriptParser::$context);
$x = array_pop($expr);
if ($x instanceof SassColour) {
$colour = $x;
} elseif ($x instanceof SassScriptOperation) {
if ($x->operator != 'concat') {
# This should never happen.
throw new SassScriptFunctionException("Couldn't parse a colour stop from: {value}", array('{value}' => $arg->value), SassScriptParser::$context->node);
}
$colour = $expr[0];
$stop = $expr[1];
} else {
throw new SassScriptFunctionException("Couldn't parse a colour stop from: {value}", array('{value}' => $arg->value), SassScriptParser::$context->node);
}
$list[] = new CompassColourStop($colour, $stop);
} else {
throw new SassScriptFunctionException('Not a valid color stop: {arg}', array('{arg}' => $arg->value), SassScriptParser::$context->node);
}
}
return new CompassList($list);
}