public AST term()
{
AST node = factor();
while (ct.t_type == "MUL" || ct.t_type == "DIV")
{
token = ct;
if (ct.t_type == "MUL")
{
verify("MUL");
}
else if (ct.t_type == "DIV")
{
verify("DIV");
}
node = new BinOp(node, token, factor());
}
return(node);
}
public AST expr()
{
AST node = term();
while (ct.t_type == "ADD" || ct.t_type == "SUB")
{
token = ct;
if (ct.t_type == "ADD")
{
verify("ADD");
}
else if (ct.t_type == "SUB")
{
verify("SUB");
}
node = new BinOp(node, token, term());
}
return(node);
}
public int visit_BinOp(BinOp node)
{
if (node.Op.t_type == "ADD")
{
return(Convert.ToInt32(visit(node.Left)) + Convert.ToInt32(visit(node.Right)));
}
else if (node.Op.t_type == "SUB")
{
return(Convert.ToInt32(visit(node.Left)) - Convert.ToInt32(visit(node.Right)));
}
else if (node.Op.t_type == "MUL")
{
return(Convert.ToInt32(visit(node.Left)) * Convert.ToInt32(visit(node.Right)));
}
else if (node.Op.t_type == "DIV")
{
return(Convert.ToInt32(visit(node.Left)) / Convert.ToInt32(visit(node.Right)));
}
return(0);
}