public function isTerminal()
    {
        if ($this instanceof NumberNode) {
            return true;
        }

        if ($this instanceof IntegerNode) {
            return true;
        }

        if ($this instanceof RationalNode) {
            return true;
        }

        if ($this instanceof VariableNode) {
            return true;
        }

        if ($this instanceof ConstantNode) {
            return true;
        }

        return false;
    }
public function isTerminal()
    {
        if ($this instanceof NumberNode) {
            return true;
        }

        if ($this instanceof IntegerNode) {
            return true;
        }

        if ($this instanceof RationalNode) {
            return true;
        }

        if ($this instanceof VariableNode) {
            return true;
        }

        if ($this instanceof ConstantNode) {
            return true;
        }

        return false;
    }
public function isTerminal ( ) { if ( $ this instanceof NumberNode ) { return true ; } if ( $ this instanceof IntegerNode ) { return true ; } if ( $ this instanceof RationalNode ) { return true ; } if ( $ this instanceof VariableNode ) { return true ; } if ( $ this instanceof ConstantNode ) { return true ; } return false ; }
Returns true if the node is a terminal node, i.e.
a NumerNode, VariableNode or ConstantNode.

@retval boolean
Returns true if the node is a terminal node i . e . a NumerNode VariableNode or ConstantNode .