public static TResult Result <TSource, TResult>(this IChild <TSource, TResult> child,
TSource source, int?firstIndex, int?lastIndex)
{
var length = child.Count(source);
if (length == 0)
{
return(child.Empty);
}
var left = firstIndex ?? 0;
if (left > length)
{
return(child.Empty);
}
if (left < 0)
{
left = length + left;
}
if (left < 0)
{
left = 0;
}
var right = lastIndex ?? length - 1;
if (right >= length)
{
return(child.Empty);
}
if (right < 0)
{
right = length + right;
}
if (right < 0)
{
right = 0;
}
if (left >= right)
{
return(child.Empty);
}
return(child.GetChilds(source, left, right));
}