(Idea) LINQ methods #153
Description
LINQ extension methods that also return the Enumerator, so that the rest of the sequence can further processed. I think that the enumerator be required to be lifted into a capture so it lifetime can persist across multiple methods.
Example: OnFirst
Tuple<IEnumerator<T>,R> OnFirst<T,R>( this IEnumerable<T> xs , initial R, Func<R,T, R> fn )
{
var en = xs.GetEnumerator();
var res = initial;
if( en.MoveNext() )
{
res = fn(res, en.Current )
return Tuple.Create(res, en );
}
return res;
}