Add each-function

src/IterTools.jl

@@ -30,7 +30,8 @@ export
     takewhile,
     properties,
     propertyvalues,
-    fieldvalues
+    fieldvalues,
+    each
 
 function has_length(it)
     it_size = IteratorSize(it)
@@ -590,14 +591,14 @@ iterate(it::StaticSizeBinomial{0}, state=false) = state ? nothing : ((), true)
 pop(t::NTuple) = reverse(tail(reverse(t))), t[end]
 
 function advance(it::StaticSizeBinomial{K}, idx) where {K}
-	xs = it.xs
-	lidx, i = pop(idx)
+    xs = it.xs
+    lidx, i = pop(idx)
     i += 1
-	if i > length(xs) - K + length(idx)
-		lidx = advance(it, lidx)
-		i = lidx[end] + 1
-	end
-	return (lidx..., i)
+    if i > length(xs) - K + length(idx)
+        lidx = advance(it, lidx)
+        i = lidx[end] + 1
+    end
+    return (lidx..., i)
 end
 advance(it::StaticSizeBinomial, idx::NTuple{1}) = (idx[end]+1,)
 
@@ -1031,4 +1032,33 @@ function iterate(fs::FieldValues, state=1)
     return (getfield(fs.x, state), state + 1)
 end
 
+"""
+    each(ElementType::Type, collection)
+
+If `collection` can be `convert`ed into `ElementType`, it is converted and wrapped in a
+`Tuple{ElementType}`. Otherwise, the *elements* of `collection` are converted into
+`ElementType`.
+
+# Examples
+```jldoctest
+julia> println.(each(Tuple, [(1, 2), (3, 4)]));
+(1, 2)
+(3, 4)
+
+julia> println.(each(Tuple, (1, 2)));
+(1, 2)
+
+julia> println.(each(String, (1, 2)));
+ERROR: MethodError: Cannot `convert` an object of type Int64 to an object of type String
+[...]
+```
+"""
+function each(::Type{T},collection) where T
+    try
+        return (convert(T,collection),)
+    catch
+        return convert.(T,collection)
+    end
+end
+
 end # module IterTools

test/runtests.jl

@@ -320,6 +320,7 @@ include("testing_macros.jl")
                 @test eltype(eltype(sk5)) == Int
                 @test length(collect(sk5)) == binomial(4, i)
             end
+            @test iterate(subsets(collect(1:4),Val{2}()),(1,4)) == ((1,4), (2,3))
 
             function collect_pairs(x)
                 p = Vector{NTuple{2, eltype(x)}}(undef, binomial(length(x), 2))
@@ -554,5 +555,12 @@ include("testing_macros.jl")
             @test IteratorSize(typeof(g)) == IteratorSize(typeof(iter))
         end
     end
+
+    @testset "each" begin
+        @test each(Tuple,[(1,2),(1,2)]) == [(1,2),(1,2)]
+        @test each(Tuple,(1,2)) == ((1,2),)
+        @test_throws MethodError each(Tuple,["something"])
+        @test eltype(each(Int32,(1,2))) == Int32
+    end
 end
 end