AL: Recursive Functions with Crystal Long

What are Recursive Functions and why would you use one? How do you design and use a recursive function? Join Crystal Long as she explores two recursive functions. Also discussions about vbNullString, Collections, and Memory. Download presentation + ACCDB databases for ListFile and RelPath https://msaccessgurus.com/presentation/Recursive_Functions.htm List files recursively by Allen Browne http://allenbrowne.com/ser-59.html 0:00 introduction by Maria Barnes for Recursive Functions 1:11 crystal 1:37 first database is Allen Browne's ListFiles application where the recursive part calls itself for subfolders to list path and filename to a collection 2:37 using the demo form to call Allen's ListFiles with save files to a table 5:38 query to show number of files for each batch filter the FileList table 6:13 add more fields to the FileList table 7:08 use to get information from Access databases List Objects, Loop files – names of Access objects https://msaccessgurus.com/tool/ListObjects_LoopFiles.htm 7:50 Concepts for Allen's code 7:57 Dir function 9:05 vbNullString 11:01 Collection object 11:37 TrailingSlash Type Declaration Character 12:31 Allen's VBA code 12:34 Call ListFiles 13:22 ListFiles 15:35 FillDir 18:54 chat about vbNullString and helpful links by Mike Wolfe The vbNullString Constant in VBA https://nolongerset.com/vbnullstring/ How to Efficiently Check for Empty Strings in VBA https://nolongerset.com/check-for-empty-strings-in-vba/ An Article About Nothing https://nolongerset.com/an-article-about-nothing/ 19:21 Save Relationship Paths - another recursive function 21:00 import table and module to use 21:39 DEMO 23:27 SaveCollectionToTable 25:10 additional error handling in FillDir 27:29 What is ASCII for each character? https://msaccessgurus.com/VBA/WhatisAscii.htm 27:55 file names 28:26 FSO File System Object https://learn.microsoft.com/en-us/office/vba/language/reference/user-interface-help/filesystemobject-object 30:08 RelPath example Relationship Paths stop VBA each time recursive function is called 31:13 information from MSysRelationships 31:48 table of relationship paths 33:04 Links 34:07 Maria - *next Lunchtime meeting* Interfacing with an Outlook Calendar 35:24 danger of recursive functions 36:40 end point to avoid infinite loop, added self-join note and stop loop 37:10 vulnerable to available memory 37:51 open discussion 38:13 Maria- recursion is a powerful technique 39:04 two different collections 40:19 Adrian - ByRef and ByVal 43:32 Maria - does anyone have a good example of where they've used recursion? 43:39 Duane - list of all my image files on a bunch of different hard drives to get rid of duplicates and find them 45:04 really like the way Crystal has taken it further to dig into Access files to find a table or function when you can't remember which file it was in 45:50 escape route infinite loop 46:24 Neil - muscle memory, stack space and consequences of running recursion Every time called, gobbles up all you've dimmed so Dim as little as possible. Keep it lean. 47:35 my question: what is the limit? If we run out of memory space with a collection, does it cache to a disk? 48:07 Adrian - memory, stack, heap 48:32 Maria - once you run out of memory, it's not very graceful. Would love to see a presentation on how to monitor memory to avoid out-of-memory errors, and keep track of when I'm getting close. 50:10 Neil - system resources 52:34 Peter - navigation control 53:09 Neil - that messes up Screen.ActiveForm because its always the navigation form because they didn't put in support on where you've navigated to 53:30 wrap-up Next Meeting: Interfacing with the Outlook calendar by Maria Barnes Tuesday March 31, 12 noon central https://accessusergroups.org/calendar/lunchtime-2-2026-03-31/ join us! related videos AL: Using Dictionaries and Collections to work with JSON in Access by Maria Barnes, Neil Sargent, Leo theDBguy (1:03:47) https://youtu.be/c7PwDuXPLeA AL: 2 free tools: 1. List Access Objects 2, VBA Code Documenter, and step-thru OpenBypass -crystal, Adrian, Peter (1:03:31) https://youtu.be/ePMIb3LuL6s Access Lunchtime Playlist on YouTube: https://www.youtube.com/playlist?list=PLwIULo1M2EWvapx3zAhd3jhX_ITigxM6M