Lazy Array iterator functions do not pass an index to the callback

[dstarke]

The standard Array iterator functions like forEach() and map() take a callback function with the signature: function(element, index, array). The Lazy Array here takes a callback with the signature: function(element). I understand why the third argument doesn't necessarily make sense in this context, but it seems like the lazy array implementation should at least accept functions of the form: function(element, index).