Dot calls / broadcasts for strings

Internals & Design
, ,
9

The SubString isn’t that what makes it slower.
But split fills up a Vector with chunks of SubString-views by traversing through the complete String searching for the next occurence of the split character. Thats how it looks like:

julia> @less split(a,"")

...
function _split(str::AbstractString, splitter::F, limit::Integer, keepempty::Bool, strs::Vector) where F
    # Forcing specialization on `splitter` improves performance (roughly 30% decrease in runtime)
    # and prevents a major invalidation risk (1550 MethodInstances)
    i = 1 # firstindex(str)
    n = lastindex(str)::Int
    r = findfirst(splitter,str)::Union{Nothing,Int,UnitRange{Int}}
    if !isnothing(r)
        j, k = first(r), nextind(str,last(r))::Int
        while 0 < j <= n && length(strs) != limit-1
            if i < k
                if keepempty || i < j
                    push!(strs, @inbounds SubString(str,i,prevind(str,j)::Int))
                end
                i = k
            end
            (k <= j) && (k = nextind(str,j)::Int)
            r = findnext(splitter,str,k)::Union{Nothing,Int,UnitRange{Int}}
            isnothing(r) && break
            j, k = first(r), nextind(str,last(r))::Int
        end
    end
    if keepempty || i <= ncodeunits(str)::Int
        push!(strs, @inbounds SubString(str,i))
    end
    return strs
end

Doesn’t look so fast, isn’t it?