Avoiding infinite loop when the search string is empty

[lorenzo]

The String.indexes function enters an infinite loop when doing String.indexes "" "Some string", this is because the i variable is no advanced on each step of the loop since it will always return 0.

I chose to return an empty list for this cases, as I think it is the most sensible thing to do IMO, but another valid interpretation is that the empty string is contained in all of the indexes of the string.

In case the second interpretation is preferred, I can gladly change it :)

[eeue56]

You should add a test to this PR.

[eeue56]

You should add a test to this PR.

[lorenzo]

@eeue56 Done

[lorenzo]

@eeue56 Done

[evancz]

Thanks, this change makes sense to me! I'm trying to sort out the contributors agreement stuff at the moment. Can you either ping the email you sent previously or fill this out and send it to me? It's looking like we'll be able to do something nicer soon, so I apologize for the inconvenience.

[evancz]

Thanks, this change makes sense to me! I'm trying to sort out the contributors agreement stuff at the moment. Can you either ping the email you sent previously or fill this out and send it to me? It's looking like we'll be able to do something nicer soon, so I apologize for the inconvenience.

[lorenzo]

@evancz Sent to your email address

[lorenzo]

@evancz Sent to your email address

[evancz]

Wouldn't it be faster to have the check for subLen > 0 outside the while loop? Seems like it only needs to happen once in an if, not on every loop.

[lorenzo]

Sure, I can do that :)

[lorenzo]

@evancz Implemented your suggestion

[lorenzo]

@evancz Implemented your suggestion

[evancz]

Better, but it can be optimized a bit more :) If you move the if above allocating i and is you can just write something like this:

if (subLen > 0)
{
    return _elm_lang$core$Native_List.Nil;
}

Which is cool in two ways. First, it means i and is do not even get allocated. Second, and more importantly, it uses the early return style, which I try to use in any C-like language. As a reader, it means I can be sure, nothing past this point is relevant to this code / some invariant is definitely true past this point.

[eeue56]

(typo: should be subLen < 1)

[lorenzo]

@evancz done

[lorenzo]

@evancz done

[evancz]

Great, thank you!

[evancz]

Great, thank you!