Moved child pointers to OperatorNode class

* access was restricted by declaring them private and offering member methods such as "hasChildren"
* only OperatorNode instances have children, there is no reason for wasting space by keeping empty pointers around in all other instances
* this enabled the removal of all nullptr comparisons from tree construction
* changed "Tree::addNode" factory method template to return a pointer to the type of the constructed node instance instead of a plain node pointer

1 files changed, 31 insertions, 5 deletions

diff --git a/src/nodes.cc b/src/nodes.cc
index 256a609..dd003c4 100644
--- a/src/nodes.cc
+++ b/src/nodes.cc
@@ -4,11 +4,20 @@
 #include "exceptions.h"
 
 #include <cmath>
+#include <cassert>
 #include <sstream>
 #include <limits>
 
 namespace SimpleParser {
 
+bool Node::hasChildren() const {
+	return false;
+}
+
+bool Node::isParentOf(Node*const) const {
+	return false;
+}
+
 OperandNode::OperandNode(double value):
 	value_{value} { }
 
@@ -31,20 +40,20 @@ OperatorNode::OperatorNode(TokenType token):
 double OperatorNode::solve() const {
 	switch ( this->operator_ ) {
 		case TokenType::OPERATOR_PLUS: {
-			return this->leftChild->solve() + this->rightChild->solve();
+			return this->left_->solve() + this->right_->solve();
 		}
 		case TokenType::OPERATOR_MINUS: {
-			return this->leftChild->solve() - this->rightChild->solve();
+			return this->left_->solve() - this->right_->solve();
 		}
 		case TokenType::OPERATOR_MULTIPLY: {
-			return this->leftChild->solve() * this->rightChild->solve();
+			return this->left_->solve() * this->right_->solve();
 		}
 		case TokenType::OPERATOR_DIVIDE: {
-			return this->leftChild->solve() / this->rightChild->solve();
+			return this->left_->solve() / this->right_->solve();
 		}
 		case TokenType::OPERATOR_POWER: {
 			return std::pow(
-				this->leftChild->solve(), this->rightChild->solve()
+				this->left_->solve(), this->right_->solve()
 			);
 		}
 		default: {
@@ -76,10 +85,27 @@ std::string OperatorNode::print() const {
 	}
 }
 
+bool OperatorNode::hasChildren() const {
+	return this->right_ != nullptr &&
+	       this->left_  != nullptr;
+}
+
+bool OperatorNode::isParentOf(Node*const node) const {
+	return this->right_ == node ||
+	       this->left_  == node;
+}
+
 TokenType OperatorNode::token() const {
 	return this->operator_;
 }
 
+void OperatorNode::setChildren(Node*const right, Node*const left) {
+	assert(right != nullptr && left != nullptr);
+
+	this->right_ = right;
+	this->left_  = left;
+}
+
 ConstantNode::ConstantNode(
 	const std::string& identifier,
 	const ConstantMap* constants