Summing the previous values in an IEnumerable

Question

I have a sequence of numbers:

var seq = new List { 1, 3, 12, 19, 33 };

and I want to transform that into a new sequence where

Answer 1

Just to offer another alternative, albeit not really LINQ, you could write a yield-based function to do the aggregation:

public static IEnumerable SumSoFar(this IEnumerable values)
{
  int sumSoFar = 0;
  foreach (int value in values)
  {
    sumSoFar += value;
    yield return sumSoFar;
  }
}

Like BrokenGlass's this makes only a single pass over the data although unlike his returns an iterator not a list.

(Annoyingly you can't easily make this generic on the numeric type in the list.)