[andybak]

I agree. Looping over a numeric sequence is simply a specific case of looping over any collection. A language should reflect this. It feels so natural to write:

    for thing in collection: process(thing)

and very easy to move from that to a functional style:

    map(collection, process)

or

    collection.map(process)

The number of times I also need a integer counter is fairly small.

[mikeash]

When you do need an integer counter, the best way to have it is to create a new collection consisting of (index, element) pairs. Swift (and many other languages) make this easy:

  for (index, element) in collection.enumerated()

There are some cases where the C style for loop is the most natural way to express something. For example, looping over NULL-terminated array of pointers is nicely expressed with one (Swift 2-ish pseudocode):

  for var cursor = ptr; cursor.pointee != nil; cursor += 1

But these situations are really rare, and when you do encounter them, it's not a big deal to transform them into a while loop:

  var cursor = ptr
  while cursor.pointee != nil {
      defer { cursor += 1 }
      ...do stuff...
  }

[masklinn]

And you can trivially package the process into an iterator anyway if it's a case you encounter often.

[mpweiher]

   result := collection collect:[ :a | a process ].
   result := collection collect process.

   collection do process.

   1 to: 10 do: [ :i | stdout println:i ].
   stdout do println: (1 to: 10).

All just plain messages and plain message syntax, no special control structures needed.