private static IParser <IReadOnlyList <T> > DoRepeat <T>(this IParser <T> parser, int atLeast, int?atMost)
{
return(Create(position =>
{
var values = new List <T>(capacity: atLeast);
var remainder = position;
int repeated = 0;
while (true)
{
if (repeated >= atMost)
{
break;
}
var result = parser.TryParse(remainder);
if (!result.Success || result.NextPosition == remainder)
{
break;
}
values.Add(result.Value);
remainder = result.NextPosition;
repeated++;
}
return repeated >= atLeast ? ParseResult.Success <IReadOnlyList <T> >(values, remainder) : ParseResult.Failure <IReadOnlyList <T> >(position);
}));
}