`indices` or `indexes`?

[eschnett]

Should Julia choose either of the terms indices or indexes as preferred when talking about arrays? From a usability point of view, it is probably desirable to choose one of the terms and stick with it, especially when it comes to name publicly visible functions in the base language or commonly used packages.

Currently, looking for either term finds about the same number of occurrences (in both local variables, argument names, and documentation combined). Some other languages (e.g. Fortran, Python) prefer indices, database systems seem to prefer indexes. Google tells me that common language prefers "indexes" while math and computer science prefer "indices".

[mbauman]

I'm terribly guilty of using both semi-interchangeably. I think I have some sort of rule in my head, where indices are abstract and indexes are a concrete collection with more than one index, but it drives me batty looking back and seeing a mix. +1 to standardizing on just one or the other.

$ ack indexes base | wc -l
      99
$ ack indices base | wc -l
      75

[jiahao]

We should stick with "indexes".

1. The Base API consistently uses "indexes", even if the internal variables, comments and docs don't always. Consider the functions localindexes and parentindexes for example.
2. Jeff's thesis uses "indexes" consistently as his personal preference.
3. "Indexes" is the more popular usage. Example: Google n-gram.
4. The major US and UK dictionaries I've consulted all list both as equivalent spellings. Note though that the OED entry states:

In current use the plural is indices in senses 8, 9, and usually in other senses except 5, in which indexes is usual.

Senses 8 and 9 refer to usage in mathematics and the sciences; 5 is the bibliographic sense (book indexes).

[tkelman]

+1 for indices

[mbauman]

I'm surprised it's weighted so heavily towards indices in registered packages:

$ ack indexes --type=julia ALL_PACKAGES | wc -l
     324
$ ack indices --type=julia ALL_PACKAGES | wc -l
    1339

I'd favor indexes. I think I tend to use indices only in prose.

[ScottPJones]

Given that indices is more the norm for math/sciences/technical meaning, and that crowd has a very high representation among Julians, I'm not surprised by that result in the registered packages (also due to the very international following that Julia has, I suppose).

[ScottPJones]

Also, some people make a distinction between database indexes, and array indices. Kind of crazy, but it happens.

[Jakki42]

Being a non-English speaker by nature indexes is significantly easier for me to notice without a single though that it's about indexing, than indices which requires slight amount of brain work to realize what it's about.

[JeffBezanson]

Down with irregular plurals!

[ScottPJones]

Flip a coin, and decide. I'll be happy to help change things either direction.

[hainm]

+1 for indices. It is a bit easier to pronounce.

[joa-quim]

In Portuguese ans Spanish (I think) it's indices, so that one is naturally easier for us.

[eschnett]

+1 for array indices as well. Fortran, Matlab, Python, R all seem to use "indices".

Note that simple searches do not give clear results, as "indexes" has a second meaning that shouldn't be counted: "the variable i indexes into the array", i.e. third person singular of the verb "to index".

[J-Sarnoff]

In matters Julia, I am greatly reluctant to advocate other than @JeffBezanson's sense of appropriateness.

with great reluctance

(This plural of index quandry is something I have examined deeply, so fwiw)
When I have more than one index, say an index of people and an index of topics then I have two indexes; when I have more than one item gathered in a well-ordered, addressable collective then I have some indices.

[kmsquire]

@J-Sarnoff's definition makes the most sense to me.