/**
* Evaluate a VariableNode
*
* Returns the current value of a VariableNode, as defined
* either by the constructor or set using the `Evaluator::setVariables()` method.
* @see Evaluator::setVariables() to define the variables
* @throws UnknownVariableException if the variable respresented by the
* VariableNode is *not* set.
*
* @param VariableNode $node AST to be evaluated
* @retval float
*/
public function visitVariableNode(VariableNode $node)
{
$name = $node->getName();
if (array_key_exists($name, $this->variables)) {
return $this->variables[$name];
}
throw new UnknownVariableException($name);
}
/**
* Print a VariableNode.
*
* @param VariableNode $node
*/
public function visitVariableNode(VariableNode $node)
{
return $node->getName();
}
/**
* Differentiate a VariableNode
*
* Create a NumberNode representing '0' or '1' depending on
* the differetiation variable.
*
* @param NumberNode $node AST to be differentiated
* @retval Node
*/
public function visitVariableNode(VariableNode $node)
{
if ($node->getName() == $this->variable) {
return new IntegerNode(1);
}
return new IntegerNode(0);
}