Generating a n-ary Cartesian product example

Question

I found that Eric Lippert\'s post here suits a particular problem I have.

The problem is I can\'t wrap my head around how I should be using it with a 2+ amount of co

Answer 1

The sample code is already able to do "n" cartesian products (it does 3 in the example). Your problem is that you have a List<List<MyType>> when you need an IEnumerable<IEnumerable<MyType>>

IEnumerable<IEnumerable<MyType>> result = collections
  .Select(list => list.AsEnumerable())
  .CartesianProduct();

Answer 2

Since List<T> is IEnumerable<T>, then your problem using Eric's solution is solved as follows:

var collections = new List<List<MyType>>();
var product =  collections.CartesianProduct();
foreach(var collection in product)
{
    // a single collection of MyType items
    foreach(var item in collection)
    {
        // each item of type MyType within a collection
        Console.Write(item);
    }    
}

Of course you can aggregate the items from each collection in a more concise manner, for example as a single string:

var product = 
    collections
    .CartesianProduct()
    .Select(xs => xs.Aggregate(new StringBuilder(), (sb, x) => sb.Append(x.ToString()), sb => sb.ToString()));

foreach(var collectionAsString in product)
{
    Console.WriteLine(collectionAsString);
}