/// <summary>
/// 执行一个表达式
/// </summary>
/// <param name="Expression">表达式语法树</param>
/// <returns>执行结果</returns>
public object ExecExpression(ASTNode_Expression Expression)
{
switch (Expression.Type)
{
case ASTNode.ASTType.BinaryExpression:
{
ASTNode_BinaryExpression tBinaryExpression = (ASTNode_BinaryExpression)Expression;
object tLeftResult = ExecExpression(tBinaryExpression.Left);
object tRightResult = ExecExpression(tBinaryExpression.Right);
return(applyBinaryOperator(tBinaryExpression.BinaryOperator, tLeftResult, tRightResult, Expression.LineNumber));
}
case ASTNode.ASTType.UnaryExpression:
{
ASTNode_UnaryExpression tUnaryExpression = (ASTNode_UnaryExpression)Expression;
object tRightResult = ExecExpression(tUnaryExpression.Right);
return(applyUnaryOperator(tUnaryExpression.UnaryOperator, tRightResult, Expression.LineNumber));
}
case ASTNode.ASTType.DigitLiteral:
{
ASTNode_DigitLiteral tDigitLiteral = (ASTNode_DigitLiteral)Expression;
return(tDigitLiteral.Value);
}
case ASTNode.ASTType.CallExpression:
{
ASTNode_CallExpression tCallExpression = (ASTNode_CallExpression)Expression;
return(applyCallOperator(
tCallExpression.Identifier,
tCallExpression.IdentifierLower,
tCallExpression.ArgList,
Expression.LineNumber
));
}
case ASTNode.ASTType.SymbolExpression:
{
ASTNode_SymbolExpression tSymbolExpression = (ASTNode_SymbolExpression)Expression;
return(fetchValueOfIdentifier(
tSymbolExpression.Identifier,
tSymbolExpression.IdentifierLower,
Expression.LineNumber
));
}
case ASTNode.ASTType.TupleExpression:
{
ASTNode_TupleExpression tTupleExpression = (ASTNode_TupleExpression)Expression;
return(calcuTupleValue(tTupleExpression, Expression.LineNumber));
}
default:
throw new RuntimeException(Expression.LineNumber, "internal error.");
}
}
/// <summary>
/// 解析原子表达式
/// </summary>
/// <param name="Lex">词法分析器</param>
/// <returns>解析结果</returns>
private static ASTNode_Expression ParseAtomExpression(Lexer Lex)
{
ASTNode_Expression tRet;
if (Lex.CurrentToken == Lexer.Token.DigitLiteral) // digit_literal
{
tRet = new ASTNode_DigitLiteral(Lex.Line, Lex.CurrentDigit);
Lex.Next();
return(tRet);
}
else if (Lex.CurrentToken == Lexer.Token.Identifier) // symbol or call_expression
{
string tIdentifier = MatchIdentifier(Lex);
// 检查下一个符号
if (TryMatchToken(Lex, Lexer.Token.LeftBracket)) // '(' -- call_expression
{
ASTNode_ArgList tArgList = ParseArgList(Lex);
MatchToken(Lex, Lexer.Token.RightBracket); // ')'
return(new ASTNode_CallExpression(Lex.Line, tIdentifier, tArgList));
}
else // symbol
{
return(new ASTNode_SymbolExpression(Lex.Line, tIdentifier));
}
}
else if (TryMatchToken(Lex, Lexer.Token.LeftBracket)) // '(' -- bracket_expression
{
tRet = ParseBracketExpression(Lex);
MatchToken(Lex, Lexer.Token.RightBracket); // ')'
return(tRet);
}
else
{
throw new SyntaxException(Lex.Position, Lex.Line, Lex.Row,
String.Format("unexpected token {0}.", Lex.FormatCurrentToken()));
}
}