15
Can't decide if end user index access should be 0 or 1 based and if END index should be inclusive (beehaw.org)
submitted 4 days ago* (last edited 4 days ago) by thingsiplay@beehaw.org to c/programming@programming.dev
19 comments fedilink hide all child comments

I'm currently writing a CLI tool that handles a specific JSON data format. And I also want to give the user to get a slice of the item array of the file. It's a slice in form of --slice START:END through commandline options. So in example --slice 1:2.

  1. Should I provide a 0 based index for the access or a 1 based index? In example --slice 1:2 with 0 based index would start with the second element and with 1 based index it would start with the first element.
  2. And would you think its better to have the END to be inclusive or exclusive? In example --slice 1:2 would get only one element if its exclusive or it gets two elements if its inclusive.

I know this is all personal taste, but I'm currently just torn between all options and cannot decide. And thought to ask you what you think. Maybe that helps me sorting my own thoughts a bit. Thanks in advance.

you are viewing a single comment's thread
view the rest of the comments
[-] thingsiplay@beehaw.org 2 points 4 days ago* (last edited 4 days ago)

I think that I'm going with these approaches. For the '0', I'm now accepting it as the 0 element. Which is not 0 based index, but it really means before the first element. So any slice with an END of 0 is always nothing. Anything that starts at 0 will basically give you as many elements as END points to.

  • 0: is equivalent to : and 1: (meaning everything)
  • 0 is equivalent to 0:0 and :0 (meaning empty)
  • 1:0 still empty, because it starts after it ended, which reads like "start by 1, give me 0 elements"
  • 1:1 gives one element, the first, which reads like "start by 1, give me 1 element"

I feel confident about this solution. And thanks for everyone here, this was really what I needed. After trying it out in the test data I have, I personally like this model. This isn't anything surprising, right?

[-] locuester@lemmy.zip 2 points 3 days ago* (last edited 3 days ago)

I personally find it easier for non programmers to use a START:LENGTH model.

3:5 is (up to) 5 elements starting at the third.

1:1 is just the first element

Any 0 is invalid

20:2 is elements 20 and 21

It eliminates inclusive/exclusive questions.

this post was submitted on 28 Jul 2025
15 points (100.0% liked)

Programming

21903 readers
338 users here now

Welcome to the main community in programming.dev! Feel free to post anything relating to programming here!

Cross posting is strongly encouraged in the instance. If you feel your post or another person's post makes sense in another community cross post into it.

Hope you enjoy the instance!

Rules

Rules

  • Follow the programming.dev instance rules
  • Keep content related to programming in some way
  • If you're posting long videos try to add in some form of tldr for those who don't want to watch videos

Wormhole

Follow the wormhole through a path of communities !webdev@programming.dev

founded 2 years ago
MODERATORS
snowe@programming.dev
Ategon@programming.dev
MaungaHikoi@lemmy.nz
UlrikHD@programming.dev