adds map for Nullable

Author: vchuravy

base/nullable.jl

@@ -56,3 +56,9 @@ function hash(x::Nullable, h::UInt)
         return hash(x.value, h + nullablehash_seed)
     end
 end
+
+# Specialised map over Nullable
+function map(f::Callable, x :: Nullable)
+    isnull(x) && return Nullable{Union()}()
+    Nullable(f(get(x)))
+end

test/nullable.jl

@@ -243,3 +243,7 @@ for T in types
     @test !isnull(x1.v)
     @test get(x1.v, one(T)) === one(T)
 end
+
+# test map
+@test map(x->x, Nullable{Union()}()) === Nullable{Union()}()
+@test map(x->x, Nullable(1.0)) === Nullable(1.0)