charstarstar.(1:2) will create new vector. So your radix_sort will sort something unnamed and temporary.
When I show address arithmetic in Julia I didn’t mean that it has to happen there. I would rather try to prepare some example (Christmas present 
) for you:
We could sort 100 millions of strings under 10s. Are we closer to R now?
This is result:
julia str_qsort.jl
before sort: String["Z", "Y", "X", "W", "V", "U", "T", "S", "R", "Q", "P", "O", "N", "M", "L", "K", "J", "I", "H", "G", "F", "E", "D", "C", "B", "A"]
488.482 ns (0 allocations: 0 bytes)
after sort: String["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]
before sort: length=100000000
it is ok now to have unordered strings! svec1[1]>svec1[2] "WIA">"Tzuk="
9.186 s (0 allocations: 0 bytes)
after sort length=100000000
sorted! :)
This is str_qsort.jl (I tested it with Julia 0.6.1 and also with 0.7.0-DEV):
using BenchmarkTools
C_code = raw"""
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int compare(const void* l, const void* r){
char* cl = *(char**)l+8;
char* cr = *(char**)r+8;
return strcmp(cl, cr);
}
void str_qsort(char **strings, size_t len) { /* you need to pass len here */
/* qsort(strings, len, sizeof(char*), (int (*)(void*, void*))strcmp); */
qsort(strings, len, sizeof(char*), compare);
}
"""
const Clib = "strqsort" # tempname() # make a temporary file
# compile to a shared library by piping C_code to gcc
# (works only if you have gcc installed):
open(`gcc -fPIC -O3 -msse3 -xc -shared -o $(Clib * "." * Libdl.dlext) -`, "w") do f
print(f, C_code)
end
# define a Julia function that calls the C function:
str_qsort(X::Array{String}) = ccall(("str_qsort", Clib), Void, (Ptr{UInt64}, Cint), reinterpret(Ptr{UInt64}, pointer(X)), length(X))
a = [String([Char(i)]) for i in 'Z':-1:'A']
println("before sort: $a")
@btime str_qsort(a)
println("after sort: $a")
const M=100_000_000; const K=100
srand(1)
svec1 = rand([string(rand(Char.(32:126), rand(1:8))...) for k in 1:M÷K], M)
l = length(svec1)
println("before sort: length=$l")
for i in 1:length(svec1)-1
if svec1[i]>svec1[i+1]
println("it is ok now to have unordered strings! svec1[$i]>svec1[$(i+1)] \"$(svec1[i])\">\"$(svec1[i+1])\"")
break
end
end
@btime str_qsort(svec1)
l = length(svec1)
println("after sort length=$l")
global sorted = true
for i in 1:length(svec1)-1
if svec1[i]>svec1[i+1]
println("error svec1[$i]>svec1[$(i+1)] $(svec1[i])>$(svec1[i+1])")
sorted = false
break
end
end
println(sorted ? "sorted! :)" : "unsorted! :(")