Array.IndexOf() has no way to search part of array

bgrommes

Problem

If I'm going to look for all occurences of some value in an Array the algorithm at present would have to be (example using Integer array):

var pos As Integer = theArray.IndexOf(searchValue)

While pos > -1
  # Do something that changes found item
  pos = theArray.IndexOf(searchValue)  
Wend

There is no reason to start the search from zero each time, but no way to specify a different starting point.
This will happen to work (at the expense of re-examining the portion of the array already examined) if I am globally changing all found values to something else but of course if that's not the case then I have to resort to perhaps an extension method or some other workaround.

Proposed Solution

Two new argument to IndexOf():
Optional startPosition As Integer = 0
Optional count As Integer = Array.Count - startPosition

Most IndexOf implementations have this. At least I can't recall one that doesn't. You should be able to search any portion of the array desired.

Garry

Good suggestion, thanks. I've implemented this in the next release: https://feedback.objo.dev/feature/569

I’ve added this to Array.IndexOf() with two new overloads:

IndexOf(item As T, startIndex As Integer) As Integer
IndexOf(item As T, startIndex As Integer, count As Integer) As Integer

The returned index is the absolute array index, not relative to the searched range.

So your original use case can now be written as:

Var pos As Integer = theArray.IndexOf(searchValue)

While pos > -1
  # Do something with pos
  pos = theArray.IndexOf(searchValue, pos + 1)
Wend

bgrommes

Garry Perfect, thanks!