Add transpose() and ctranspose()

These used to be provided by DataArrays, and are needed to transpose an
Array{Union{T, Null}} since these functions are called recursively.

src/Nulls.jl

@@ -63,7 +63,7 @@ for f in (:(!), :(+), :(-), :(Base.identity), :(Base.zero),
           :(Base.log2), :(Base.exponent), :(Base.sqrt), :(Base.gamma), :(Base.lgamma),
           :(Base.iseven), :(Base.ispow2), :(Base.isfinite), :(Base.isinf), :(Base.isodd),
           :(Base.isinteger), :(Base.isreal), :(Base.isimag), :(Base.isnan), :(Base.isempty),
-          :(Base.iszero))
+          :(Base.iszero), :(Base.transpose), :(Base.ctranspose))
     @eval $(f)(d::Null) = null
 end
 
@@ -84,7 +84,8 @@ end
 for f in (:(Base.ceil), :(Base.floor), :(Base.round), :(Base.trunc))
     @eval begin
         ($f)(::Null, digits::Integer=0, base::Integer=0) = null
-        ($f)(::Type, ::Null) = null
+        ($f)(::Type{>:Null}, ::Null) = null
+        ($f)(::Type, ::Null) = throw(NullException())
     end
 end
 

test/runtests.jl

@@ -33,7 +33,7 @@ using Base.Test, Nulls
                             iseven, isodd, ispow2,
                             isfinite, isinf, isnan, iszero,
                             isinteger, isreal, isimag,
-                            isempty]
+                            isempty, transpose, ctranspose]
 
     rounding_functions = [ceil, floor, round, trunc]
 
@@ -52,7 +52,8 @@ using Base.Test, Nulls
         @test isnull(f(null))
         @test isnull(f(null, 1))
         @test isnull(f(null, 1, 1))
-        @test isnull(f(Int, null))
+        @test isnull(f(Union{Int, Null}, null))
+        @test_throws NullException f(Int, null)
     end
 
     @test zero(Union{Int, Null}) === 0