You could also implement the short-circuiting one recursively:
function findocc(f, A, i)
i == 1 && return findfirst(f, A)
findnext(f, A, findocc(f, A, i - 1) + 1)
end
julia> A = [1:10...]
10-element Array{Int64,1}:
1
2
3
4
5
6
7
8
9
10
julia> findocc(x->iseven(x), A, 3)
6
julia> findocc(x->iseven(x), A, 5)
10
julia> findocc(x->iseven(x), A, 6)
0
On Friday, July 17, 2015 at 10:07:47 AM UTC-4, David Gold wrote:
>
> If you don't care about short-circuiting after finding the nth occurrence
> you could of course just do `find(f, A)[n]`.
>
> On Friday, July 17, 2015 at 10:00:43 AM UTC-4, Pontus Stenetorp wrote:
>>
>> Everyone,
>>
>> I just recently needed to find the index of the n-th occurrence of a
>> predicate an Array and was a bit surprised that there was not a
>> convenience function in Base. Rolling one on your own is simple, but
>> I somehow expected to find something in Base to get the same
>> functionality.
>>
>> function findocc(testf::Function, A, n)
>> i = 0
>> for _ in 1:n
>> i = findnext(testf, A, i + 1)
>> i != 0 || return 0
>> end
>> return i
>> end
>>
>> Am I perhaps missing something that is already supported in Base? [1]
>> If not, I may consider yet another small pull request. But as always
>> with these small convenience functions I fear that I am missing
>> something obvious that already supports the same functionality.
>>
>> Pontus
>>
>> [1]:
>> http://julia.readthedocs.org/en/latest/stdlib/arrays/?highlight=find#Base.find
>>
>>
>
