private AST Term()
{
var node = Factor();
while (currentToken.TokenType == TokenType.MUL ||
currentToken.TokenType == TokenType.INTEGER_DIV ||
currentToken.TokenType == TokenType.FLOAT_DIV)
{
var token = currentToken;
if (token.TokenType == TokenType.MUL)
{
Eat(TokenType.MUL);
}
else if (token.TokenType == TokenType.INTEGER_DIV)
{
Eat(TokenType.INTEGER_DIV);
}
else if (token.TokenType == TokenType.FLOAT_DIV)
{
Eat(TokenType.FLOAT_DIV);
}
node = new BinOp(left: node, op: token, right: Factor());
}
return(node);
}
public override int VisitBinOp(BinOp node)
{
if (node.op.TokenType == TokenType.PLUS)
{
return(Visit(node.left) + Visit(node.right));
}
if (node.op.TokenType == TokenType.MINUS)
{
return(Visit(node.left) - Visit(node.right));
}
if (node.op.TokenType == TokenType.MUL)
{
return(Visit(node.left) * Visit(node.right));
}
if (node.op.TokenType == TokenType.DIV)
{
return(Visit(node.left) / Visit(node.right));
}
throw new Exception("Unknown node!");
}
public AST Expr()
{
var node = Term();
while (currentToken.TokenType == TokenType.PLUS || currentToken.TokenType == TokenType.MINUS)
{
var token = currentToken;
if (token.TokenType == TokenType.PLUS)
{
Eat(TokenType.PLUS);
}
if (token.TokenType == TokenType.MINUS)
{
Eat(TokenType.MINUS);
}
node = new BinOp(left: node, op: token, right: Term());
}
return(node);
}
public override object VisitBinOp(BinOp node)
{
if (node.op.TokenType == TokenType.PLUS)
{
return((double)Visit(node.left) + (double)Visit(node.right));
}
if (node.op.TokenType == TokenType.MINUS)
{
return((double)Visit(node.left) - (double)Visit(node.right));
}
if (node.op.TokenType == TokenType.MUL)
{
return((double)Visit(node.left) * (double)Visit(node.right));
}
if (node.op.TokenType == TokenType.INTEGER_DIV)
{
return(double.Parse(Visit(node.left).ToString()) / double.Parse(Visit(node.right).ToString()));
}
if (node.op.TokenType == TokenType.FLOAT_DIV)
{
return((double)Visit(node.left) / (double)Visit(node.right));
}
throw new Exception("Unknown node!");
}
public abstract int VisitBinOp(BinOp op);
public abstract object VisitBinOp(BinOp op);