/*
* 语法解析：乘法表达式
* **/
private SimpleASTNode multiplicative(ITokenReader tokens)
{
SimpleASTNode child1 = primary(tokens);
SimpleASTNode node = child1;
IToken token = tokens.peek();
if (child1 != null && token != null)
{
if (token.getType() == TokenType.Star || token.getType() == TokenType.Slash)
{
token = tokens.read();
SimpleASTNode child2 = primary(tokens);
if (child2 != null)
{
node = new SimpleASTNode(ASTNodeType.Multiplicative, token.getText());
node.addChild(child1);
node.addChild(child2);
}
else
{
throw (new FormatException("无效的乘法表达式!"));
}
}
}
return(node);
}
/*
* 语法解析：根节点
* **/
private SimpleASTNode prog(ITokenReader tokens)
{
SimpleASTNode node = new SimpleASTNode(ASTNodeType.Programm, "Calculator");
SimpleASTNode child = additive(tokens);
if (child != null)
{
node.addChild(child);
}
return(node);
}
/*
* 整型变量声明语句，如：int a; int b = 2*3;
* **/
private SimpleASTNode intDeclare(ITokenReader tokens)
{
SimpleASTNode node = null;
IToken token = tokens.peek();
if (token.getType() == TokenType.Int)
{
tokens.read();
token = tokens.peek();
if (token.getType() == TokenType.Identifier)
{
token = tokens.read();
node = new SimpleASTNode(ASTNodeType.IntDeclaration, token.getText());
token = tokens.peek();
if (token.getType() == TokenType.Assignment)
{
tokens.read();
SimpleASTNode child = additive(tokens);
if (child != null)
{
node.addChild(child);
}
else
{
throw (new FormatException("'='赋值表达式错误"));
}
}
}
else
{
throw (new FormatException("需要一个变量名"));
}
if (node != null)
{
token = tokens.peek();
if (token != null && token.getType() == TokenType.SemiColon)
{
tokens.read();
}
else
{
throw (new FormatException("表达式缺少分号"));
}
}
}
return(node);
}