implement sortperm (#773)

Author: stev47

src/SOneTo.jl

@@ -15,6 +15,8 @@ function SOneTo{n}(r::AbstractUnitRange) where n
     errmsg(r)
 end
 
+Base.Tuple(::SOneTo{N}) where N = ntuple(identity, Val(N))
+
 Base.axes(s::SOneTo) = (s,)
 Base.size(s::SOneTo) = (length(s),)
 Base.length(s::SOneTo{n}) where {n} = n

src/sort.jl

@@ -1,5 +1,5 @@
-import Base.Order: Ordering, Forward, ReverseOrdering, ord
-import Base.Sort: Algorithm, lt, sort
+import Base.Order: Forward, Ordering, Perm, ReverseOrdering, ord
+import Base.Sort: Algorithm, lt, sort, sortperm
 
 
 struct BitonicSortAlg <: Algorithm end
@@ -23,20 +23,36 @@ defalg(a::StaticVector) =
     return _sort(a, alg, ordr)
 end
 
+@inline function sortperm(a::StaticVector;
+               alg::Algorithm = defalg(a),
+               lt = isless,
+               by = identity,
+               rev::Union{Bool,Nothing} = nothing,
+               order::Ordering = Forward)
+    p = Tuple(axes(a, 1))
+    length(a) <= 1 && return SVector{length(a),Int}(p)
+
+    ordr = Perm(ord(lt, by, rev, order), a)
+    return SVector{length(a),Int}(_sort(p, alg, ordr))
+end
+
+
 @inline _sort(a::StaticVector, alg, order) =
     similar_type(a)(sort!(Base.copymutable(a); alg=alg, order=order))
 
 @inline _sort(a::StaticVector, alg::BitonicSortAlg, order) =
     similar_type(a)(_sort(Tuple(a), alg, order))
 
+_sort(a::NTuple, alg, order) = sort!(Base.copymutable(a); alg=alg, order=order)
+
 # Implementation loosely following
 # https://www.inf.hs-flensburg.de/lang/algorithmen/sortieren/bitonic/oddn.htm
 @generated function _sort(a::NTuple{N}, ::BitonicSortAlg, order) where N
     function swap_expr(i, j, rev)
         ai = Symbol('a', i)
         aj = Symbol('a', j)
         order = rev ? :revorder : :order
-        return :( ($ai, $aj) = lt($order, $ai, $aj) ? ($ai, $aj) : ($aj, $ai) )
+        return :( ($ai, $aj) = @inbounds lt($order, $ai, $aj) ? ($ai, $aj) : ($aj, $ai) )
     end
 
     function merge_exprs(idx, rev)

test/sort.jl

@@ -19,4 +19,12 @@ using StaticArrays, Test
         end
     end
 
+    @testset "sortperm" for T in (Int, Float64)
+        for N in (0, 1, 2, 3, 10, 20, 30)
+            v = rand(SVector{N,T})
+            vp = sortperm(v)
+            @test v[vp] == sort(v)
+        end
+    end
+
 end