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Refactor

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Jim
2023-08-31 22:03:17 +01:00
parent 9c5bf4c0d5
commit eaeb64b314
3 changed files with 160 additions and 133 deletions
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74
MathEngine/MathEngine/Evaluator/Evaluator.cs Normal file
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@@ -0,0 +1,74 @@
using MathEngine.Parser.Parser;
using MathEngine.Parser.Tokeniser;
namespace MathEngine.Parser.Evaluator
{
/// <summary>
///
/// </summary>
internal class Evaluator
{
public static TreeNode? Evaluate(TreeNode rootNode)
{
if (rootNode == null)
{
return null;
}
else // To evaluate we go anti-clockwise around the tree
{
TreeNode? Root, LeftBranch, RightBranch;
if (rootNode.NodeValue.Token_Type == Token.Type.Numeric)
return rootNode;
else
{ //For now these can't be null, this will need to be updated in the future
LeftBranch = Evaluate_Tree_Branch(rootNode.GetChildNode(0));
RightBranch = Evaluate_Tree_Branch(rootNode.GetChildNode(1));
Root = Evaluate_Operator(rootNode.NodeValue, LeftBranch, RightBranch);
return Root;
}
}
}
/// <summary>
/// Evaluates branches of a given tree
/// </summary>
/// <param name="Branch">The TreeNode branch to evaluate</param>
/// <returns>Returns the Evaluation of the Branch</returns>
private static TreeNode Evaluate_Tree_Branch(TreeNode Branch)
{
TreeNode Root, LeftBranch, RightBranch;
if (Branch.NodeValue.Token_Type == Token.Type.Numeric)
return Branch;
else
{
LeftBranch = Evaluate_Tree_Branch(Branch.GetChildNode(0));
RightBranch = Evaluate_Tree_Branch(Branch.GetChildNode(1));
// We finally combine the computed branches with the operator that links them and return the result
Root = Evaluate_Operator(Branch.NodeValue, LeftBranch, RightBranch);
return Root;
}
}
/// <summary>
/// Evlautes a binary node where the root node is an operator and given two branches the left and the right
/// </summary>
/// <param name="Operator_Token"></param>
/// <param name="Left_Branch"></param>
/// <param name="Right_Branch"></param>
/// <returns>Returns the evaluated value of the operator as a TreeNode</returns>
private static TreeNode Evaluate_Operator(Token Operator_Token, TreeNode Left_Branch, TreeNode Right_Branch)
{
decimal lhs = decimal.Parse(Left_Branch.NodeValue.TokenValue);
decimal rhs = decimal.Parse(Right_Branch.NodeValue.TokenValue);
return Operator_Token.Token_Type switch
{
Token.Type.Addition => new TreeNode(new Token((lhs + rhs).ToString(), Token.Type.Numeric, Token.NumericType.Decimal, 0)),
Token.Type.Subtraction => new TreeNode(new Token((lhs - rhs).ToString(), Token.Type.Numeric, Token.NumericType.Decimal, 0)),
Token.Type.Multiplication => new TreeNode(new Token(((decimal)(lhs * rhs)).ToString(), Token.Type.Numeric, Token.NumericType.Decimal, 0)),
Token.Type.Division => new TreeNode(new Token(((decimal)(lhs / rhs)).ToString(), Token.Type.Numeric, Token.NumericType.Decimal, 0)),
_ => throw new Exception("Potentially invalid token?"),
};
}
}
}

138
MathEngine/MathEngine/Parser/Parser/ExpressionTree.cs
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@@ -1,5 +1,4 @@
using System.Collections.Generic; using MathEngine.Parser.Tokeniser;
using MathEngine.Parser.Tokeniser;
namespace MathEngine.Parser.Parser namespace MathEngine.Parser.Parser
{ {
/// <summary> /// <summary>
@@ -11,6 +10,7 @@ namespace MathEngine.Parser.Parser
/// The root node of the expression tree; /// The root node of the expression tree;
/// </summary> /// </summary>
private readonly TreeNode rootNode; private readonly TreeNode rootNode;
private TreeNode? evaluated_expression;
/// <summary> /// <summary>
/// Initialises a new instance of the MathEngine.Parser.Parser.Node class with a given Token /// Initialises a new instance of the MathEngine.Parser.Parser.Node class with a given Token
@@ -21,7 +21,7 @@ namespace MathEngine.Parser.Parser
{ {
List<Token> tokens = Tokeniser.Tokeniser.Tokenise(Expression); List<Token> tokens = Tokeniser.Tokeniser.Tokenise(Expression);
Stack<Token> rpnForm = Parser.Parse(tokens); Stack<Token> rpnForm = Parser.Parse(tokens);
rootNode = GenerateExpressionTree(rpnForm); rootNode = TreeGenerator.TreeFromRPN(rpnForm);
} }
private ExpressionTree(TreeNode rootNode) private ExpressionTree(TreeNode rootNode)
@@ -29,141 +29,13 @@ namespace MathEngine.Parser.Parser
this.rootNode = rootNode; this.rootNode = rootNode;
} }
/// <summary>
/// Creates a binary TreeNode, that is a node with a root value and two children
/// </summary>
/// <param name="CurrentToken">The token to be the root node of the TreeNode</param>
/// <param name="LeftToken">TreeNode that is the left branch of the current node</param>
/// <param name="RightToken">TreeNode that is the right branch of the current node</param>
/// <returns>A TreeNode with CurrentToken as the root value and LeftBranch and RightBranch as Children</returns>
private static TreeNode CreateBinaryNode(Token CurrentToken, TreeNode LeftBranch, TreeNode RightBranch)
{
TreeNode root = new(CurrentToken);
root.AddChildNode(LeftBranch);
root.AddChildNode(RightBranch);
return root;
}
/// <summary>
/// Creates a unary TreeNode, that is a node with a root value and two children
/// </summary>
/// <param name="CurrentToken">The token to be the root node of the TreeNode</param>
/// <param name="LeftToken">TreeNode that is the child of the current node</param>
/// <returns>A TreeNode with CurrentToken as the root value and ChildNode as the sole child node</returns>
private static TreeNode CreateUnaryNode(Token CurrentToken, TreeNode ChildNode)
{
TreeNode root = new(CurrentToken);
root.AddChildNode(ChildNode);
return root;
}
/// <summary>
/// Generates the full expression tree given an RPN expression stack
/// </summary>
/// <param name="rpnExpression">RPN expression stack to generate an expression tree from</param>
/// <returns>An expression Tree that represents the Mathematical expression given by rpnExpression</returns>
private static TreeNode GenerateExpressionTree(Stack<Token> rpnExpression)
{
Stack<TreeNode> OutputStack = new(rpnExpression.Count);
TreeNode Node;
Token CurrentToken;
while (rpnExpression.Count != 0)
{
CurrentToken = rpnExpression.Pop();
switch (CurrentToken.Token_Type)
{
case Token.Type.Numeric:
Node = new TreeNode(CurrentToken);
OutputStack.Push(Node);
break;
// We need to preserve "Left handness" of the ExpressionTree
// i.e 7/8 gives a root node of / with Cnode(0) = 7 and Cnod(1) = 8 etc.
// This should preserve non commutativity
case Token.Type.Addition:
case Token.Type.Subtraction:
case Token.Type.Multiplication:
case Token.Type.Division:
case Token.Type.Exponentiation:
TreeNode Right = OutputStack.Pop();
TreeNode Left = OutputStack.Pop();
Node = CreateBinaryNode(CurrentToken, Left, Right);
OutputStack.Push(Node);
break;
case Token.Type.UnaryPlus:
case Token.Type.UnaryMinus:
Node = CreateUnaryNode(CurrentToken, OutputStack.Pop());
OutputStack.Push(Node);
break;
}
}
return OutputStack.Pop();
}
/// <summary>
/// Evaluates branches of a given tree
/// </summary>
/// <param name="Branch">The TreeNode branch to evaluate</param>
/// <returns>Returns the Evaluation of the Branch</returns>
private static TreeNode Evaluate_Tree_Branch(TreeNode Branch)
{
TreeNode Root, LeftBranch, RightBranch;
if (Branch.NodeValue.Token_Type == Token.Type.Numeric)
return Branch;
else
{
LeftBranch = Evaluate_Tree_Branch(Branch.GetChildNode(0));
RightBranch = Evaluate_Tree_Branch(Branch.GetChildNode(1));
// We finally combine the computed branches with the operator that links them and return the result
Root = Evaluate_Operator(Branch.NodeValue, LeftBranch, RightBranch);
return Root;
}
}
/// <summary>
/// Evlautes a binary node where the root node is an operator and given two branches the left and the right
/// </summary>
/// <param name="Operator_Token"></param>
/// <param name="Left_Branch"></param>
/// <param name="Right_Branch"></param>
/// <returns>Returns the evaluated value of the operator as a TreeNode</returns>
private static TreeNode Evaluate_Operator(Token Operator_Token, TreeNode Left_Branch, TreeNode Right_Branch)
{
decimal lhs = decimal.Parse(Left_Branch.NodeValue.TokenValue);
decimal rhs = decimal.Parse(Right_Branch.NodeValue.TokenValue);
return Operator_Token.Token_Type switch
{
Token.Type.Addition => new TreeNode(new Token((lhs + rhs).ToString(), Token.Type.Numeric, Token.NumericType.Decimal, 0)),
Token.Type.Subtraction => new TreeNode(new Token((lhs - rhs).ToString(), Token.Type.Numeric, Token.NumericType.Decimal, 0)),
Token.Type.Multiplication => new TreeNode(new Token(((decimal)(lhs * rhs)).ToString(), Token.Type.Numeric, Token.NumericType.Decimal, 0)),
Token.Type.Division => new TreeNode(new Token(((decimal)(lhs / rhs)).ToString(), Token.Type.Numeric, Token.NumericType.Decimal, 0)),
_ => throw new Exception("Potentially invalid token?"),
};
}
/// <summary> /// <summary>
/// Evaluates the current instance of ExpressionTree /// Evaluates the current instance of ExpressionTree
/// </summary> /// </summary>
/// <returns>Returns an update of the current instance which the expression Evaluated</returns> /// <returns>Returns an update of the current instance which the expression Evaluated</returns>
public ExpressionTree? Evaluate() public ExpressionTree Evaluate()
{ {
if (rootNode == null) return new(Evaluator.Evaluator.Evaluate(rootNode));
{
return null;
}
else // To evaluate we go anti-clockwise around the tree
{
TreeNode? Root, LeftBranch, RightBranch;
if (rootNode.NodeValue.Token_Type == Token.Type.Numeric)
return this;
else
{ //For now these can't be null, this will need to be updated in the future
LeftBranch = Evaluate_Tree_Branch(rootNode.GetChildNode(0));
RightBranch = Evaluate_Tree_Branch(rootNode.GetChildNode(1));
Root = Evaluate_Operator(rootNode.NodeValue, LeftBranch, RightBranch);
return new ExpressionTree(Root);
}
}
} }
/// <summary> /// <summary>

81
MathEngine/MathEngine/Parser/Parser/TreeGenerator.cs Normal file
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@@ -0,0 +1,81 @@
using MathEngine.Parser.Tokeniser;
namespace MathEngine.Parser.Parser
{
/// <summary>
/// Class for converting from RPN form to an expression tree
/// </summary>
internal class TreeGenerator
{
/// <summary>
/// Creates a binary TreeNode, that is a node with a root value and two children
/// </summary>
/// <param name="CurrentToken">The token to be the root node of the TreeNode</param>
/// <param name="LeftToken">TreeNode that is the left branch of the current node</param>
/// <param name="RightToken">TreeNode that is the right branch of the current node</param>
/// <returns>A TreeNode with CurrentToken as the root value and LeftBranch and RightBranch as Children</returns>
private static TreeNode CreateBinaryNode(Token CurrentToken, TreeNode LeftBranch, TreeNode RightBranch)
{
TreeNode root = new(CurrentToken);
root.AddChildNode(LeftBranch);
root.AddChildNode(RightBranch);
return root;
}
/// <summary>
/// Creates a unary TreeNode, that is a node with a root value and two children
/// </summary>
/// <param name="CurrentToken">The token to be the root node of the TreeNode</param>
/// <param name="LeftToken">TreeNode that is the child of the current node</param>
/// <returns>A TreeNode with CurrentToken as the root value and ChildNode as the sole child node</returns>
private static TreeNode CreateUnaryNode(Token CurrentToken, TreeNode ChildNode)
{
TreeNode root = new(CurrentToken);
root.AddChildNode(ChildNode);
return root;
}
/// <summary>
/// Generates the full expression tree given an RPN expression stack
/// </summary>
/// <param name="rpnExpression">RPN expression stack to generate an expression tree from</param>
/// <returns>An expression Tree that represents the Mathematical expression given by rpnExpression</returns>
public static TreeNode TreeFromRPN(Stack<Token> rpnExpression)
{
Stack<TreeNode> OutputStack = new(rpnExpression.Count);
TreeNode Node;
Token CurrentToken;
while (rpnExpression.Count != 0)
{
CurrentToken = rpnExpression.Pop();
switch (CurrentToken.Token_Type)
{
case Token.Type.Numeric:
Node = new TreeNode(CurrentToken);
OutputStack.Push(Node);
break;
// We need to preserve "Left handness" of the ExpressionTree
// i.e 7/8 gives a root node of / with Cnode(0) = 7 and Cnod(1) = 8 etc.
// This should preserve non commutativity
case Token.Type.Addition:
case Token.Type.Subtraction:
case Token.Type.Multiplication:
case Token.Type.Division:
case Token.Type.Exponentiation:
TreeNode Right = OutputStack.Pop();
TreeNode Left = OutputStack.Pop();
Node = CreateBinaryNode(CurrentToken, Left, Right);
OutputStack.Push(Node);
break;
case Token.Type.UnaryPlus:
case Token.Type.UnaryMinus:
Node = CreateUnaryNode(CurrentToken, OutputStack.Pop());
OutputStack.Push(Node);
break;
}
}
return OutputStack.Pop();
}
}
}