/// <summary>
/// Context-preserving variant of <see cref="SourceOperations.Grouped{TOut,TMat}"/>
/// Each output group will be associated with a `Seq` of corresponding context elements.
/// </summary>
public static SourceWithContext <IReadOnlyList <TCtx>, IReadOnlyList <TOut>, TMat> Grouped <TCtx, TOut, TMat>(
this SourceWithContext <TCtx, TOut, TMat> flow, int n)
{
var stage = new Grouped <(TOut, TCtx)>(n);
return(flow.Via(Flow.FromGraph(stage).Select(itemsWithContexts =>
{
var items = new List <TOut>(n);
var ctxs = new List <TCtx>(n);
foreach (var tuple in itemsWithContexts)
{
items.Add(tuple.Item1);
ctxs.Add(tuple.Item2);
}
return ((IReadOnlyList <TOut>)items, (IReadOnlyList <TCtx>)ctxs);
})));
}
/// <summary>
/// Context-preserving variant of <see cref="SourceOperations.SelectMany{T,TOut,TMat}"/>.
/// The context of the input element will be associated with each of the output elements calculated from
/// this input element.
/// </summary>
public static SourceWithContext <TCtx, TOut2, TMat> SelectConcat <TCtx, TOut, TOut2, TMat>(
this SourceWithContext <TCtx, TOut, TMat> flow, Func <TOut, IEnumerable <TOut2> > fn) =>
StatefulSelectConcat(flow, () => fn);
