Identifying last loop when using for each

Question

I want to do something different with the last loop iteration when performing 'foreach' on an object. I'm using Ruby but the same goes for C#, Java etc.

  list = ['A','B','C']   list.each{|i|     puts "Looping: "+i # if not last loop iteration     puts "Last one: "+i # if last loop iteration   } 

The output desired is equivalent to:

  Looping: 'A'   Looping: 'B'   Last one: 'C' 

The obvious workaround is to migrate the code to a for loop using 'for i in 1..list.length', but the for each solution feels more graceful. What is the most graceful way to code a special case during a loop? Can it be done with foreach?

Answer 1

I see a lot of complex, hardly readable code here... why not keep it simple:

var count = list.Length;  foreach(var item in list)     if (--count > 0)         Console.WriteLine("Looping: " + item);     else         Console.Writeline("Lastone: " + item); 

It's only one extra statement!

Another common situation is that you want to do something extra or less with the last item, like putting a separator between the items:

var count = list.Length;  foreach(var item in list) {     Console.Write(item);     if (--count > 0)         Console.Write(","); } 

Answer 2

The foreach construct (in Java definitely, probably also in other languages) is intended to represent the most general kind if iteration, which includes iteration over collections that have no meaningful iteration order. For example, a hash-based set does not have an ordering, and therefore there is no "last element". The last iteration may yield a different element each time you iterate.

Basically: no, the foreach construct is not meant to be used that way.