private StringScannerEngine ExpectImpl(IExpectPattern pattern)
{
AssertNotFinished();
CachePos();
AutoSkipWhitespace();
int startPos = Index;
pattern.Initialize(Index, Chars);
// call the function one more time after the end of the string - this determines outcome
if (pattern.Validate())
{
Match = pattern.Result;
NewPos(pattern.EndIndex);
}
else
{
Index = pattern.EndIndex; // for error report to be accurate - will be undone at end
ThrowUnexpectedCharacterException();
}
return(this);
}
