findfirst , findlast and findall differences in needles

[oxinabox]

findfirst, findlast and findall each support a different set of needles when the haystack is an AbstractString.

findfirst(::Union{Regex, AbstractString, Function, AbstractChar}, ::AbstractString)
# Everything

findall(::Union{Regex, AbstractString, Function}, ::AbstractString)
# No AbstractChar

findlast(::Union{AbstractString, Function, AbstractChar}, ::AbstractString)
# No Regex

We should make them consistent

[nalimilan]

See also findnext and findprev, which are respectively consistent with findfirst and findlast.

I'm not sure it's possible to get the last match of a regex with PCRE. That question may not be well-defined, as one can also write a regex to extract the last match of an expression, and pass that to findfirst. Of course as a brute-force method we could have findlast return last(findall(...)), but that's not a good implementation.

[stevengj]

Yes, PCRE doesn't support reverse-order searching. (You can simulate by reversing the string and searching with a reversed regex, but automatically constructing a reversed regex in general seems to be a hard problem.)