/**
* Evaluate a SassScript.
* @param string expression to parse
* @param SassContext the context in which the expression is evaluated
* @param integer 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 ($token instanceof SassScriptFunction) {
array_push($operands, $token->perform());
} elseif ($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 array_shift($operands);
}
