> For example, one would often like an IIndexable interface to cover both arrays and lists I’ve thought about this. To be useful, an IIndexable would need get

> For example, one would often like an IIndexable interface to cover both arrays and lists I’ve thought about this. To be useful, an IIndexable would need get and set methods for the index, and a Length/Count property. You would need to explicitly implement it on something like the array class since you wouldn’t want to lose the semantic difference between Length (O(1)) and Count (O(n)). But, the existence of Func<T, TResult> and Action<T1, T2> would largely obsolete the utility of such and interface. Let xs be an “indexable” object of T (e.g. T[] or List<T>). Then any method that expects to only access an object could just accept lambda of type int -> T. So, you’d just pass it n => xs[n]. Similarly, methods that expect to mutate the object could take a lambda of type (int, T) -> (). So would just pass something like (n, x) => xs[n] = x. This is nicer because it makes explicit what the method will do to the indexable.