At a first glance, Back() seems to be the equivalent to First(). One gets the first element of an array, the other gets the last element. But there are two important differences:
First() has two signatures, it works on arrays and feature sets
Back() only has one signature, it doesn't work on feature sets
The behavior when called on an empty array is different:
var arr = []
var f_arr = First(arr) // f_arr is null
var b_arr = Back(arr) // this will throw an ExecutionError
This has implications for guarding against empty arrays (or featuresets):
var arr = []
// some code that fills arr (or doesn't)
// when we want to goard against an empty array using First(), we can simply
// call the function and check the result for null:
var f_arr = First(arr)
if(f_arr == null) {
// arr is empty, code for that case here
} else {
// arr isn't empty
}
// when we want to do the same using Back(), we have to call Count(), which
// is more computationally intensive, especially for large array
if(Count(arr) == 0) {
// arr is empty, code for that case here
} else {
// arr isn't empty
}
For most arrays, this is probably negligible, but it could very well become a problem if Back() could work on feature sets. Also, it's just irritating that these two quite similar functions handle this case so differently.
So, my suggestion:
- Enable Back() to work on feature sets
- Change how Back() handles empty input to how First() does it
- optionally, rename Back() to Last(), because that's what it does: it gets the last element, in the same way that First() gets the first element and isn't named Front()...
