Expression CreateBinaryExpression(Node node)
{
Expression left = CreateExpressionCore(node.Children[0]);
Expression right = CreateExpressionCore(node.Children[1]);
if (left == null || right == null)
{
return null;
}
switch (node.Kind)
{
case NodeType.Addition:
return Expression.Add(left, right);
case NodeType.Subtraction:
return Expression.Subtract(left, right);
case NodeType.Multiplication:
return Expression.Multiply(left, right);
case NodeType.Division:
return Expression.Divide(left, right);
case NodeType.Power:
return Expression.Power(left, right);
}
return null;
}
public Expression<Func<double, double>> CreateFunction(Node root, CompileResult status)
{
Status = status;
ParameterExpression parameter = Expression.Parameter(typeof(double), "x");
Binder.RegisterParameter(parameter);
Expression body = CreateExpressionCore(root);
if (body == null)
{
return null;
}
var expressionTree = Expression.Lambda<Func<double, double>>(body, parameter);
return expressionTree;
}
public Expression<Func<double>> CreateExpression(Node root, CompileResult status)
{
Status = status;
Expression body = CreateExpressionCore(root);
if (body == null)
{
return null;
}
// If expression does not return double, we'll get an error.
if (body.Type != typeof(double))
{
return null;
}
var expressionTree = Expression.Lambda<Func<double>>(body);
return expressionTree;
}
Expression CreateCallExpression(Node root)
{
string functionName = root.Token.Text;
MethodInfo method = Binder.ResolveMethod(functionName);
if (method == null)
{
Status.AddMethodNotFoundError(functionName);
return null;
}
var arguments = root.Children;
if (arguments.Count == 1)
{
var argument = CreateExpressionCore(arguments[0]);
if (argument == null)
{
return null;
}
return Expression.Call(method, argument);
}
Status.AddMethodNotFoundError(functionName);
return null;
}
Expression CreatePropertyAccessExpression(Node root)
{
string propertyName = root.Children[1].Token.Text;
var argument = CreateExpressionCore(root.Children[0]);
if (argument == null)
{
return null;
}
Type type = argument.Type;
var property = type.GetRuntimeProperty(propertyName);
if (property == null)
{
Status.AddBindError(propertyName);
return null;
}
var propertyExpression = Expression.Property(argument, property);
return propertyExpression;
}
Expression CreateUnaryExpression(Node root)
{
Expression operand = CreateExpressionCore(root.Children[0]);
if (operand == null)
{
return null;
}
return Expression.Negate(operand);
}
Expression CreateExpressionCore(Node root)
{
switch (root.Kind)
{
case NodeType.Negation:
return CreateUnaryExpression(root);
case NodeType.Addition:
case NodeType.Subtraction:
case NodeType.Multiplication:
case NodeType.Division:
case NodeType.Power:
return CreateBinaryExpression(root);
case NodeType.Variable:
return CreateIdentifierExpression(root);
case NodeType.Constant:
return CreateLiteralExpression(Convert.ToDouble(root.Token.Text));
case NodeType.FunctionCall:
return CreateCallExpression(root);
case NodeType.PropertyAccess:
return CreatePropertyAccessExpression(root);
default:
return null;
}
}
Expression CreateIdentifierExpression(Node root)
{
var text = root.Token.Text;
var parameter = Binder.Resolve(text);
if (parameter == null)
{
Status.AddUnknownIdentifierError(text);
}
return parameter;
}
private Node PropertyAccess(Node left, Node right)
{
return new Node(NodeType.PropertyAccess, left, right);
}
private Node ParseFunctionCall()
{
var result = new Node(NodeType.FunctionCall, Current);
AdvanceToken();
AdvanceToken(TokenType.OpenParen);
AddArgument(result, ParseExpression());
while (CurrentTokenKind == TokenType.Comma)
{
AdvanceToken();
AddArgument(result, ParseExpression());
}
AdvanceToken(TokenType.CloseParen);
return result;
}
private Node Negation(Node unaryOperand)
{
return new Node(NodeType.Negation, unaryOperand);
}
private Node BinaryOperator(NodeType operationType, Node leftOperand, Node rightOperand)
{
return new Node(operationType, leftOperand, rightOperand);
}
private void AddArgument(Node functionCall, Node argument)
{
functionCall.Children.Add(argument);
}