Implement get for CleverDict (#1153)

* Implement get for CleverDict

* Add tests when `is_dense` is `true`

Author: blegat

src/Utilities/CleverDicts.jl

@@ -26,7 +26,7 @@ Provided no keys are deleted, the backing storage is a `Vector{V}`. Once a key
 has been deleted, the backing storage switches to an `OrderedDict{K, V}`.
 
 Use the `add_item` to enforce adding item in sequence. Once an object is added
-out of order `add_item` does not work anymore and the storage is switched to 
+out of order `add_item` does not work anymore and the storage is switched to
 `OrderedDict{K, V}` if it is not one already.
 
 The i'th ordered element can be obtained with `c[LinearIndex(i)]`.
@@ -149,6 +149,16 @@ function Base.haskey(c::CleverDict{K}, key::K) where K
         return Base.haskey(c.dict, key)
     end
 end
+function Base.get(c::CleverDict, key, default)
+    if _is_dense(c)
+        if !haskey(c, key)
+            return default
+        end
+        return c.vector[c.hash(key)::Int64]
+    else
+        return get(c.dict, key, default)
+    end
+end
 function Base.getindex(c::CleverDict, key)
     if _is_dense(c)
         if !haskey(c, key)

test/Utilities/CleverDicts.jl

@@ -20,6 +20,10 @@ CleverDicts.index_to_key(::Type{MyKey}, index::Int) = MyKey{index}()
         d = CleverDicts.CleverDict{MathOptInterface.VariableIndex, String}()
         key = CleverDicts.add_item(d, "first")
         @test key == MathOptInterface.VariableIndex(1)
+        @test get(d, key, nothing) == "first"
+        @test get(d, MathOptInterface.VariableIndex(2), nothing) === nothing
+        @test Dict(key => "first") == d
+        @test Dict(key => "second") != d
         sizehint!(d, 1)
         @test d[key] == "first"
         @test haskey(d, key) == true
@@ -35,6 +39,10 @@ CleverDicts.index_to_key(::Type{MyKey}, index::Int) = MyKey{index}()
         @test d[key2] == "second"
         d[key2] = "third"
         @test d[key2] == "third"
+        @test get(d, key, nothing) === nothing
+        @test get(d, key2, nothing) === "third"
+        @test Dict(key2 => "second") != d
+        @test Dict(key2 => "third") == d
 
         empty!(d)