Single naming convention for functions returning indices in 2.0

[jariji]

There are multiple naming conventions for search functions

• findfirst, findall return indices
• findmin/findmax return (value, key) pairs (who ever heard of a (value, key) pair?)
• searchsorted{,first,last} return indices
• indmin/indmax (PR) return indices

I suggest find as a "returns indices" convention in 2.0.

[Seelengrab]

The indmax/indmin PR in question

[nalimilan]

+1

See previous discussions at #10593 and the Search & Find Julep. The problems raised here are indeed the parts of the Julep that didn't end up being implemented in Julia 1.0. In particular, #25414 is about searchsorted*, #24865 about findmin/findmax.

[jariji]

Edit: This comment doesn't make sense.

findfirst takes a function as the first argument but searchsorted takes the function as by=, like sort. It would be nice to not have different APIs for essentially similar functions. I think that would mean choosing either do or by= for both find* and sort*, but that might not be worth it.

[aplavin]

searchsorted's by is not really equivalent to findfirst's first argument (needle).
It would be nice to support predicates in searchsorted, like searchsortedfirst(≥(x), xs) (currently it's searchsortedfirst(xs, x)), searchsortedfirst(>(x), xs), searchsortedfirst(==(x), xs), searchsortedfirst(∈(x:y), xs). These variants are arguably as useful as ≥(x), but currently require careful bookkeeping from the user's part.

As we are talking about major changes anyway, searchsorted would be more composable as findfirst(≥(x), Sorted(xs)) with Sorted being a simple wrapper. This way, libraries would just use findfirst and it will work with arbitrary collections (linear search) and sorted collections (binary search).