private static ResultCode MakeImplicitMultiplications(
ExpressionOptions options, List <Token> tokens)
{
for (int i = 0; i < tokens.Count; i++)
{
var token = tokens[i];
if (token is CollectionToken collectionToken)
{
var code = MakeImplicitMultiplications(options, collectionToken.Children);
if (code != ResultCode.Ok)
{
return(code);
}
}
else if (token.Type != TokenType.Name)
{
// Skip as this type is not allowed to have an implicit factor prefix.
continue;
}
if (i - 1 < 0)
{
continue; // We are at the list's beginning.
}
var leftToken = tokens[i - 1];
if (leftToken.Type == TokenType.Operator ||
leftToken.Type == TokenType.Name ||
leftToken.Type == TokenType.ListSeparator)
{
continue;
}
if (leftToken.Type != TokenType.DecimalDigit &&
leftToken.Type != TokenType.DecimalNumber &&
leftToken.Type != TokenType.List)
{
return(ResultCode.InvalidTokenBeforeList);
}
var multiplyOpDef = options.GetOperatorDefinition(OperatorType.Multiply);
if (multiplyOpDef == null)
{
return(ResultCode.MissingMultiplicationDefinition);
}
var opToken = new ValueToken(TokenType.Operator, multiplyOpDef.Names[0]);
tokens.Insert(i, opToken);
}
return(ResultCode.Ok);
}
public static EError?ValidateOperatorTokens(
ExpressionOptions options, ValueToken op, Token?left, Token?right)
{
var opDef = options.GetOperatorDefinition(op.Value);
if (opDef != null)
{
if (left == null && (
opDef.Associativity == OperatorSidedness.Both ||
opDef.Associativity.HasFlag(OperatorSidedness.Left)))
{
return(EErrorCode.OperatorMissingLeftValue);
}
if (right == null && (
opDef.Associativity == OperatorSidedness.Both ||
opDef.Associativity.HasFlag(OperatorSidedness.Right)))
{
return(EErrorCode.OperatorMissingRightValue);
}
}
return(null);
}
private static ResultCode MakeOperatorGroups(ExpressionOptions options, List <Token> tokens)
{
var listStack = new Stack <List <Token> >();
listStack.Push(tokens);
var opIndices = new List <(int index, ValueToken token, OperatorDefinition definition)>();
var opShifts = new List <(int index, int shift)>();
while (listStack.Count > 0)
{
var currentTokens = listStack.Pop();
for (int j = 0; j < currentTokens.Count; j++)
{
var token = currentTokens[j];
if (token is CollectionToken collectionToken)
{
listStack.Push(collectionToken.Children);
}
}
// Gather operators so we can sort them by priority rules.
opIndices.Clear();
for (int j = 0; j < currentTokens.Count; j++)
{
var token = currentTokens[j];
if (token.Type != TokenType.Operator)
{
continue;
}
var opToken = (ValueToken)token;
var opDef = options.GetOperatorDefinition(opToken.Value);
if (opDef == null)
{
return(ResultCode.UnknownSymbol);
}
opIndices.Add((index: j, opToken, opDef));
}
opIndices.Sort((x, y) =>
{
int xPriority = x.definition?.Precedence ?? 0;
int yPriority = y.definition?.Precedence ?? 0;
// Sort types in descending order.
int priorityCompare = yPriority.CompareTo(xPriority);
if (priorityCompare != 0)
{
return(priorityCompare);
}
// Sort indices of same type in ascending order.
return(x.index.CompareTo(y.index));
});
// Merge token triplets with a center operator or
// pairs with a leading operator.
opShifts.Clear();
for (int i = 0; i < opIndices.Count; i++)
{
var(opIndex, opToken, opDef) = opIndices[i];
// Offset "opIndex" by shifts caused by previous operator merges.
for (int j = 0; j < opShifts.Count; j++)
{
var(shiftIndex, shift) = opShifts[j];
if (shiftIndex < opIndex)
{
opIndex += shift;
}
}
Token?leftToken = null;
Token?rightToken = null;
int left = opIndex - 1;
if (opDef?.Associativity != OperatorSidedness.Right)
{
if (left < 0)
{
if (opDef != null && opDef.Associativity.HasFlag(OperatorSidedness.Left))
{
return(ResultCode.OperatorMissingLeftValue);
}
}
else
{
leftToken = currentTokens[left];
}
}
if (leftToken?.Type == TokenType.Operator)
{
continue;
}
int right = opIndex + 1;
if (opDef != null && opDef.Associativity != OperatorSidedness.Left)
{
if (right >= currentTokens.Count)
{
if (opDef.Associativity.HasFlag(OperatorSidedness.Right))
{
return(ResultCode.OperatorMissingRightValue);
}
}
else
{
rightToken = currentTokens[right];
if (rightToken.Type == TokenType.Operator)
{
continue;
}
// Mitigates operators with following operators.
if (rightToken.Type == TokenType.Operator)
{
int secondRight = opIndex + 2;
if (secondRight < currentTokens.Count)
{
var subToken = new ListToken(new List <Token>(2)
{
rightToken,
currentTokens[secondRight]
});
rightToken = subToken;
currentTokens[right] = rightToken;
currentTokens.RemoveAt(secondRight);
opShifts.Add((right, -1));
opIndices.RemoveAll(x => x.index == right);
}
else
{
return(ResultCode.OperatorMissingRightValue);
}
}
}
}
int sideTokenCount = 0;
if (leftToken != null)
{
sideTokenCount++;
}
if (rightToken != null)
{
sideTokenCount++;
}
// Try to skip making a 1-item list.
int resultCount = 1 + sideTokenCount;
if (resultCount == currentTokens.Count)
{
continue;
}
var resultList = new List <Token>(resultCount);
if (leftToken != null)
{
resultList.Add(leftToken);
}
resultList.Add(opToken);
if (rightToken != null)
{
resultList.Add(rightToken);
}
int firstIndex = opIndex - (leftToken != null ? 1 : 0);
var resultToken = new ListToken(resultList);
currentTokens[firstIndex] = resultToken;
currentTokens.RemoveRange(firstIndex + 1, resultList.Count - 1);
int nextShift = 1 - resultList.Count;
opShifts.Add((opIndex, nextShift));
}
}
return(ResultCode.Ok);
}
