/// <summary>
/// Parses a group, searching for any reference and dereference operators. Operators and operands are
/// replaced with the reference/dereferenced value.
/// </summary>
/// <param name="group">The group to parse.</param>
/// <param name="limit">The index of the group to parse up to. Used by the ParseAssignmentGroup method.</param>
/// <returns>A TException on failure, otherwise null.</returns>
TException ParseReferencesOfGroup(Group group, int limit = -1)
{
int limitToUse = limit < 0 ? group.Count - 1 : limit;
int index;
while (true)
{
// Search from right to left for the first reference or dereference character
int refIndex = group.LastIndexOf(TType.REFERENCE_CHARACTER.ToString(), limitToUse),
derefIndex = group.LastIndexOf(TType.DEREFERENCE_CHARACTER.ToString(), limitToUse);
char character; // Used so we know what operation we're carrying out later
if (refIndex < 0)
{
index = derefIndex;
character = TType.DEREFERENCE_CHARACTER;
}
else if (derefIndex < 0)
{
index = refIndex;
character = TType.REFERENCE_CHARACTER;
}
else
{
if (refIndex > derefIndex)
{
index = refIndex;
character = TType.REFERENCE_CHARACTER;
}
else
{
index = derefIndex;
character = TType.DEREFERENCE_CHARACTER;
}
}
if (index < 0) break;
if (index + 1 > group.Count)
return new TException(this, "Invalid expression term '" + character + "' at end of statement");
// If the operand is not a variable, return a TException (can't dereference values)
TType variable = TType.Parse(this, group[index + 1]);
if (variable is TException) return variable as TException;
if (!(variable is TVariable))
{
if (character == TType.REFERENCE_CHARACTER)
return new TException(this,
"Attempted creation of reference to value", "expected variable identifier");
else
return new TException(this, "Attempted dereference of value", "expected variable identifier");
}
if (character == TType.REFERENCE_CHARACTER) group[index] = new TVariable("reference", variable);
else
{
group[index] = ((TVariable)variable).Value;
if (!(group[index] is TVariable) && !(group[index] is TFunction))
return new TException(this,
"Dereference of value type variable", "expected reference");
}
group.RemoveAt(index + 1);
limitToUse = limit < 0 ? group.Count - 1 : limit;
}
return null;
}
