public static (AstNode node, int numRead) Next(IEnumerable <ParseToken> tokens)
{
var originalTokens = tokens.ToList();
var toParse = originalTokens;
var(lhs, skipCount) = NextValue(toParse);
toParse = toParse.Skip(skipCount).ToList();
while (toParse.Any())
{
if (toParse[0].Type == ParseTokenType.Add || toParse[0].Type == ParseTokenType.Multiply)
{
var type = toParse[0].Type;
toParse = toParse.Skip(1).ToList();
var rhs = NextValue(toParse);
if (type == ParseTokenType.Add)
{
lhs = new AstAdd(lhs, rhs.node);
}
else
{
lhs = new AstMultiply(lhs, rhs.node);
}
toParse = toParse.Skip(rhs.numRead).ToList();
}
else
{
throw new Exception("Unexpected token type.");
}
}
return(lhs, originalTokens.Count);
}
public static (AstNode node, int numRead) Next(IEnumerable <ParseToken> tokens)
{
var originalTokens = tokens.ToList();
var toParse = originalTokens;
var(node, skipCount) = NextValue(toParse);
toParse = toParse.Skip(skipCount).ToList();
var valueList = new List <AstNode> {
node
};
var operators = new List <ParseToken>();
while (toParse.Any())
{
if (toParse[0].Type != ParseTokenType.Add && toParse[0].Type != ParseTokenType.Multiply)
{
throw new Exception("Unexpected value.");
}
operators.Add(toParse[0]);
toParse = toParse.Skip(1).ToList();
(node, skipCount) = NextValue(toParse);
valueList.Add(node);
toParse = toParse.Skip(skipCount).ToList();
}
foreach (var opToReplace in operators
.Select((op, idx) => (op.Type, idx))
.Reverse()
.Where(p => p.Type == ParseTokenType.Add)
.ToList())
{
var lhs = valueList[opToReplace.idx];
var rhs = valueList[opToReplace.idx + 1];
var newOp = new AstAdd(lhs, rhs);
operators.RemoveAt(opToReplace.idx);
valueList.RemoveAt(opToReplace.idx + 1);
valueList[opToReplace.idx] = newOp;
}
var firstValue = valueList.First();
return(valueList.Skip(1).Aggregate(firstValue, (lhs, rhs) => new AstMultiply(lhs, rhs)), originalTokens.Count);
}
