Implemented constant identifier functionality

* SimpleParser optionally acceps a pointer to an ConstantMap containing string keys mapping to values
* Constants are handled in their own ConstantNode class derived from the standard Node class
* Operator precedence is now determined separated from the TokenType using a new PrecedenceLevel enum
** Conversion between tokens and their PrecedenceLevel is possible using the new utility function getPrecedence
* Added additional test cases for constant identifier resolutions

8 files changed, 104 insertions, 26 deletions

diff --git a/src/exceptions.h b/src/exceptions.h
index cd76368..b17f424 100644
--- a/src/exceptions.h
+++ b/src/exceptions.h
@@ -24,6 +24,13 @@ class divide_exception: public std::exception {
 	}
 };
 
+class identifier_exception: public std::exception {
+	virtual const char* what() const throw()
+	{
+		return "Identifier could not be correctly resolved.";
+	}
+};
+
 }
 
 #endif  // PARSER_SRC_EXCEPTIONS_H_
diff --git a/src/nodes.cc b/src/nodes.cc
index 1ab1502..9ef0e6a 100644
--- a/src/nodes.cc
+++ b/src/nodes.cc
@@ -1,5 +1,6 @@
 #include "nodes.h"
 #include "utils.h"
+#include "tree.h"
 #include "exceptions.h"
 
 #include <cmath>
@@ -94,11 +95,22 @@ TokenType OperatorNode::getToken() {
 	return this->operator_;
 }
 
-ConstantNode::ConstantNode(std::string identifier):
-	identifier_(identifier) { }
+ConstantNode::ConstantNode(std::string identifier,
+                           const ConstantMap* constants):
+	identifier_(identifier),
+	constants_(constants) { }
 
 double ConstantNode::solve() {
-
+	if ( this->constants_ != nullptr ) {
+		try {
+			return this->constants_->at(this->identifier_);
+		}
+		catch ( std::out_of_range &e ) {
+			throw identifier_exception();
+		}
+	} else {
+		throw identifier_exception();
+	}
 }
 
 NodeType ConstantNode::getType() {
diff --git a/src/nodes.h b/src/nodes.h
index 6783f3d..170b88f 100644
--- a/src/nodes.h
+++ b/src/nodes.h
@@ -1,11 +1,13 @@
 #ifndef PARSER_SRC_NODES_H_
 #define PARSER_SRC_NODES_H_
 
+#include <map>
 #include <string>
 
 namespace SimpleParser {
 
-enum class TokenType : int8_t;
+enum class TokenType;
+typedef std::map<std::string, double> ConstantMap;
 
 enum class NodeType {
 	OPERAND,
@@ -53,7 +55,7 @@ class OperandNode: public Node {
 
 class ConstantNode: public Node {
 	public:
-		explicit ConstantNode(std::string);
+		explicit ConstantNode(std::string, const ConstantMap*);
 
 		virtual double solve();
 		virtual NodeType getType();
@@ -61,6 +63,7 @@ class ConstantNode: public Node {
 
 	private:
 		std::string identifier_;
+		const ConstantMap* constants_;
 };
 
 }
diff --git a/src/parser.h b/src/parser.h
index 89c0493..d3cdbe1 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -3,10 +3,15 @@
 
 #include <string>
 
+#include "tree.h"
+
 namespace SimpleParser {
 
 double calculate(std::string);
+double calculate(std::string, const ConstantMap*);
+
 std::string print(std::string);
+std::string print(std::string, const ConstantMap*);
 
 }
 
diff --git a/src/tree.cc b/src/tree.cc
index f6d2282..7cc3fe8 100644
--- a/src/tree.cc
+++ b/src/tree.cc
@@ -18,7 +18,14 @@ Node* topNodeFrom(const std::stack<Node*>& stack) {
 }
 
 Tree::Tree(std::string term):
-	term_(term) {
+	term_(term),
+	constants_(nullptr) {
+	this->root_node_ = this->buildTree(term);
+}
+
+Tree::Tree(std::string term, const ConstantMap* constants):
+	term_(term),
+	constants_(constants) {
 	this->root_node_ = this->buildTree(term);
 }
 
@@ -114,7 +121,7 @@ Node* Tree::buildTree(std::string term) {
 					static_cast<OperatorNode*>(topNodeFrom(operatorStack))
 				);
 
-				if ( token > lastNode->getToken() ) {
+				if ( getPrecedence(token) > getPrecedence(lastNode->getToken()) ) {
 					operatorStack.push( 
 						this->addNode<OperatorNode>(nullptr, token)
 					);
@@ -142,7 +149,8 @@ Node* Tree::buildTree(std::string term) {
 
 			if ( tmpLexer.size() == 1 ) {
 				switch ( getTokenType(tmpLexer[0][0]) ) {
-					case TokenType::VALUE_NUMBER: {
+					case TokenType::VALUE_NUMBER:
+					case TokenType::OPERATOR_MINUS: {
 						double value;
 						std::istringstream convertStream(tmpLexer[0]);
 						convertStream >> value;
@@ -155,7 +163,9 @@ Node* Tree::buildTree(std::string term) {
 					}
 					case TokenType::VALUE_IDENTIFIER: {
 						operandStack.push(
-							this->addNode<ConstantNode>(nullptr, tmpLexer[0])
+							this->addNode<ConstantNode>(nullptr,
+							                            tmpLexer[0],
+							                            this->constants_)
 						);
 
 						break;
diff --git a/src/tree.h b/src/tree.h
index 68a31c1..0db1404 100644
--- a/src/tree.h
+++ b/src/tree.h
@@ -1,17 +1,20 @@
 #ifndef PARSER_SRC_NODE_H_
 #define PARSER_SRC_NODE_H_
 
-#include <vector>
-#include <string>
 #include <memory>
+#include <string>
+#include <vector>
 
 #include "nodes.h"
 
 namespace SimpleParser {
 
+typedef std::vector<std::unique_ptr<Node>> NodeCollection;
+
 class Tree {
 	public:
 		Tree(std::string);
+		Tree(std::string, const ConstantMap*);
 
 		double solve();
 		std::string print();
@@ -21,9 +24,10 @@ class Tree {
 		Node* addNode(Node**, Args&&... args);
 		Node* buildTree(std::string);
 
-		std::vector<std::unique_ptr<Node>> node_collection_;
-		Node* root_node_;
 		std::string term_;
+		Node* root_node_;
+		NodeCollection node_collection_;
+		const ConstantMap* constants_;
 };
 
 }
diff --git a/src/utils.cc b/src/utils.cc
index 4e2ed91..9a081f3 100644
--- a/src/utils.cc
+++ b/src/utils.cc
@@ -12,9 +12,9 @@ TokenType getTokenType(char tmp) {
 	} else {
 		switch ( tmp ) {
 			case '-':
-				return TokenType::OPERATOR_PLUS;
-			case '+':
 				return TokenType::OPERATOR_MINUS;
+			case '+':
+				return TokenType::OPERATOR_PLUS;
 			case '/':
 				return TokenType::OPERATOR_DIVIDE;
 			case '*':
@@ -33,6 +33,33 @@ TokenType getTokenType(char tmp) {
 	}
 }
 
+PrecedenceLevel getPrecedence(TokenType token) {
+	switch ( token ) {
+		case TokenType::VALUE_NUMBER:
+		case TokenType::VALUE_IDENTIFIER: {
+			return PrecedenceLevel::FIRST;
+		}
+		case TokenType::OPERATOR_MINUS:
+		case TokenType::OPERATOR_PLUS: {
+			return PrecedenceLevel::SECOND;
+		}
+		case TokenType::OPERATOR_DIVIDE:
+		case TokenType::OPERATOR_MULTIPLY: {
+			return PrecedenceLevel::THIRD;
+		}
+		case TokenType::OPERATOR_POWER: {
+			return PrecedenceLevel::FOURTH;
+		}
+		case TokenType::PARENTHESES_OPEN:
+		case TokenType::PARENTHESES_CLOSE: {
+			return PrecedenceLevel::FIFTH;
+		}
+		default: {
+			return PrecedenceLevel::FIRST;
+		}
+	}
+}
+
 std::vector<std::string> lexer(std::string term) {
 	std::string tmp;
 	std::string tmpNumber;
@@ -55,7 +82,8 @@ std::vector<std::string> lexer(std::string term) {
 			if ( level > 0 ) {
 				tmp += *termIter;
 			} else {
-				if ( token == TokenType::VALUE_NUMBER ) {
+				if ( token == TokenType::VALUE_NUMBER ||
+				     token == TokenType::OPERATOR_MINUS ) {
 					tmpNumber += *termIter;
 				} else if ( token == TokenType::VALUE_IDENTIFIER ) {
 					tmpIdentifier += *termIter;
diff --git a/src/utils.h b/src/utils.h
index 9727d6a..0145065 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -8,19 +8,28 @@
 
 namespace SimpleParser {
 
-enum class TokenType : int8_t {
-	OPERATOR_PLUS     = 10,
-	OPERATOR_MINUS    = 11,
-	OPERATOR_DIVIDE   = 20,
-	OPERATOR_MULTIPLY = 21,
-	OPERATOR_POWER    = 30,
-	PARENTHESES_OPEN  = 90,
-	PARENTHESES_CLOSE = 91,
-	VALUE_NUMBER      = -1,
-	VALUE_IDENTIFIER  = -2,
+enum class PrecedenceLevel : uint8_t {
+	FIRST  = 1,
+	SECOND = 2,
+	THIRD  = 3,
+	FOURTH = 4,
+	FIFTH  = 5,
+};
+
+enum class TokenType {
+	OPERATOR_PLUS,
+	OPERATOR_MINUS,
+	OPERATOR_DIVIDE,
+	OPERATOR_MULTIPLY,
+	OPERATOR_POWER,
+	PARENTHESES_OPEN,
+	PARENTHESES_CLOSE,
+	VALUE_NUMBER,
+	VALUE_IDENTIFIER,
 };
 
 TokenType getTokenType(char);
+PrecedenceLevel getPrecedence(TokenType);
 std::vector<std::string> lexer(std::string);
 
 }