private Expression _PrimaryExpression()
{
if (Current.TokenKind == TokenKind.StringStart)
return _ReadString();
else if (Current.TokenKind == TokenKind.ID)
{
Token id = _Consume();
Expression exp = null;
// if ( follows ID, we have a function call
if (Current.TokenKind == TokenKind.LParen)
{
_Consume(); // consume LParen
Expression[] args = _ReadArguments();
_Consume(TokenKind.RParen);
exp = new FCall(id.Line, id.Col, id.Data, args);
}
else // else, we just have id
exp = new Name(id.Line, id.Col, id.Data);
// while we have ".", keep chaining up field access or method call
while (Current.TokenKind == TokenKind.Dot || Current.TokenKind == TokenKind.LBracket)
{
if (Current.TokenKind == TokenKind.Dot)
{
_Consume(); // consume DOT
Token field = _Consume(TokenKind.ID); // consume ID after dot
// if "(" after ID, then it's a method call
if (Current.TokenKind == TokenKind.LParen)
{
_Consume(); // consume "("
Expression[] args = _ReadArguments();
_Consume(TokenKind.RParen); // read ")"
exp = new MethodCall(field.Line, field.Col, exp, field.Data, args);
}
else
exp = new FieldAccess(field.Line, field.Col, exp, field.Data);
}
else // must be LBracket
{
// array access
Token bracket = Current;
_Consume(); // consume [
Expression indexExp = _TopExpression();
_Consume(TokenKind.RBracket);
exp = new ArrayAccess(bracket.Line, bracket.Col, exp, indexExp);
}
}
return exp;
}
else if (Current.TokenKind == TokenKind.Integer)
{
int value = Int32.Parse(Current.Data);
IntLiteral intLiteral = new IntLiteral(Current.Line, Current.Col, value);
_Consume(); // consume int
return intLiteral;
}
else if (Current.TokenKind == TokenKind.Double)
{
double value = Double.Parse(Current.Data);
DoubleLiteral dLiteral = new DoubleLiteral(Current.Line, Current.Col, value);
_Consume(); // consume int
return dLiteral;
}
else if (Current.TokenKind == TokenKind.LParen)
{
_Consume(); // eat (
Expression exp = _TopExpression();
_Consume(TokenKind.RParen); // eat )
return exp;
}
else
throw new ParseException("意外的 Token 表达式：" + Current.TokenKind + "。Token类型 即非 ID 也非 string。", Current.Line, Current.Col);
}
/// <summary>
/// 执行数组访问，并返回执行结果。
/// </summary>
/// <param name="arrayAccess">指定一个数组实例。</param>
/// <returns>object</returns>
protected object EvalArrayAccess(ArrayAccess arrayAccess)
{
object obj = this.EvalExpression(arrayAccess.Exp);
object index = this.EvalExpression(arrayAccess.Index);
if (obj is Array)
{
Array array = (Array)obj;
if (index is Int32)
return array.GetValue((int)index);
else
throw new TemplateRuntimeException("数组索引必须是整形数字。", arrayAccess.Line, arrayAccess.Col);
}
else
return this.EvalMethodCall(obj, "get_Item", new object[] { index });
}
