private AstNode ParseLogicalAndExpression() {
var expr = ParseEqualityExpression();
again:
var token = IsMatch(TokenKind.AndSign);
if (token != null) {
var right = ParseEqualityExpression();
expr = new BinaryAstNode(expr, token, right);
goto again;
}
return expr;
}
private AstNode ParseKeywordLogicalExpression() {
var expr = ParseKeywordNotExpression();
again:
var token = IsMatch(TokenKind.Or, TokenKind.And);
if (token != null) {
var right = ParseKeywordNotExpression();
expr = new BinaryAstNode(expr, token, right);
goto again;
}
return expr;
}
public override object VisitBinary(BinaryAstNode node) {
var left = Evaluate(node.Left);
if (left.IsError)
return left;
var right = Evaluate(node.Right);
if (right.IsError)
return right;
switch (node.Token.Kind) {
case TokenKind.Plus:
return EvaluateArithmetic(left, right, (a, b) => Result(a.Int32Value + b.Int32Value));
case TokenKind.Minus:
return EvaluateArithmetic(left, right, (a, b) => Result(a.Int32Value - b.Int32Value));
case TokenKind.Mul:
return EvaluateArithmetic(left, right, (a, b) => Result(a.Int32Value * b.Int32Value));
case TokenKind.Div:
return EvaluateArithmetic(left, right, (a, b) => b.Int32Value == 0 ? Error("Attempted to divide by zero.") : Result(a.Int32Value / b.Int32Value));
case TokenKind.And:
case TokenKind.AndSign:
return EvaluateLogicalAnd(left, right);
case TokenKind.Or:
case TokenKind.OrSign:
return EvaluateLogicalOr(left, right);
case TokenKind.EqualEqual:
return EvaluateEquality(left, right, v => v);
case TokenKind.NotEqual:
return EvaluateEquality(left, right, v => !v);
case TokenKind.LessThan:
return EvaluateComparison(left, right, v => v < 0);
case TokenKind.LessThanEqual:
return EvaluateComparison(left, right, v => v <= 0);
case TokenKind.GreaterThan:
return EvaluateComparison(left, right, v => v > 0);
case TokenKind.GreaterThanEqual:
return EvaluateComparison(left, right, v => v >= 0);
default:
throw new InvalidOperationException(string.Format("Internal error: binary operator '{0}' is not supported.", node.Token.Kind));
}
}
public virtual object VisitBinary(BinaryAstNode node) {
return null;
}
private AstNode ParseComparisonExpression() {
var expr = ParseAdditiveExpression();
var token =
IsMatch(TokenKind.LessThan, TokenKind.LessThanEqual) ??
IsMatch(TokenKind.GreaterThan, TokenKind.GreaterThanEqual);
if (token != null) {
var right = ParseComparisonExpression();
expr = new BinaryAstNode(expr, token, right);
}
return expr;
}
private AstNode ParseEqualityExpression() {
var expr = ParseComparisonExpression();
var token = IsMatch(TokenKind.EqualEqual, TokenKind.NotEqual);
if (token != null) {
var right = ParseEqualityExpression();
expr = new BinaryAstNode(expr, token, right);
}
return expr;
}
private AstNode ParseMultiplicativeExpression() {
var expr = ParseUnaryExpression();
again:
var token = IsMatch(TokenKind.Mul, TokenKind.Div);
if (token != null) {
var right = ParseUnaryExpression();
expr = new BinaryAstNode(expr, token, right);
goto again;
}
return expr;
}
public virtual object VisitBinary(BinaryAstNode node)
{
return(null);
}