Merge pull request LaboratoryOfPlasmaPhysics#13 from Dekken/const

pure const dict access method

include/dict.hpp

@@ -17,13 +17,14 @@
 
 namespace cppdict
 {
-namespace  {
+namespace
+{
     template<typename T1, typename... T2>
     constexpr bool is_any_of()
     {
         return std::disjunction_v<std::is_same<T1, T2>...>;
     }
-}
+} // namespace
 
 namespace // Visitor details
 {
@@ -103,8 +104,9 @@ struct Dict
     using data_t       = std::variant<empty_leaf_t, node_t, Types...>;
 
     template<typename T>
-    struct is_value : std::conditional<!std::is_same_v<T, empty_leaf_t> and !std::is_same_v<T, node_t>,
-                                       std::true_type, std::false_type>::type
+    struct is_value
+        : std::conditional<!std::is_same_v<T, empty_leaf_t> and !std::is_same_v<T, node_t>,
+                           std::true_type, std::false_type>::type
     {
     };
     template<typename T>
@@ -131,6 +133,7 @@ struct Dict
         return *this;
     }
     Dict& operator=(Dict&& other) = default;
+
     Dict& operator[](const std::string& key)
     {
 #ifndef NDEBUG
@@ -161,6 +164,24 @@ struct Dict
     }
 
 
+    Dict& operator[](const std::string& key) const
+    {
+        if (isNode())
+        {
+            auto& map = std::get<node_t>(data);
+
+            if (std::end(map) == map.find(key))
+            {
+                throw std::runtime_error("cppdict: invalid key: " + key);
+            }
+
+            return *std::get<node_t>(data).at(key);
+        }
+
+        throw std::runtime_error("cppdict: invalid key: " + key);
+    }
+
+
     bool isLeaf() const noexcept { return !isNode() && !isEmpty(); }
 
     bool isNode() const noexcept { return std::holds_alternative<node_t>(data); }
@@ -206,10 +227,7 @@ struct Dict
         throw std::runtime_error("cppdict: not a map or not default");
     }
 
-    bool contains(std::string key)
-    {
-        return isNode() and std::get<node_t>(data).count(key);
-    }
+    bool contains(std::string key) { return isNode() and std::get<node_t>(data).count(key); }
 
     std::size_t size() const noexcept
     {

test/basic_dict_ops.cpp

@@ -12,16 +12,16 @@ TEST_CASE("Can (depp)copy nodes with operator=", "[simple cppdict::Dict<int, dou
 {
     Dict dict;
     dict["this"]["is"]["the"]["source"] = 3.14;
-    dict["destination"] = dict["this"];
-    REQUIRE(dict["destination"]["is"]["the"]["source"].to<double>()==3.14);
+    dict["destination"]                 = dict["this"];
+    REQUIRE(dict["destination"]["is"]["the"]["source"].to<double>() == 3.14);
 }
 
 TEST_CASE("Can add values and retrieve them", "[simple cppdict::Dict<int, double, std::string>]")
 {
     Dict dict;
-    dict["first"] = 3.14;
+    dict["first"]  = 3.14;
     dict["second"] = 1;
-    dict["third"] = std::string{"hello"};
+    dict["third"]  = std::string{"hello"};
     SECTION("Added values should be retrievable")
     {
         REQUIRE(dict["first"].to<double>() == 3.14);
@@ -40,43 +40,43 @@ TEST_CASE("Can add values and retrieve them", "[simple cppdict::Dict<int, double
     }
 }
 
-TEST_CASE("Deals with both references and values", "[simple cppdict::Dict<int, double, std::string>]")
+TEST_CASE("Deals with both references and values",
+          "[simple cppdict::Dict<int, double, std::string>]")
 {
     Dict dict;
-    dict["0"]["1"] = 3.5;
-    dict["0"]["2"]["1"] = 55.;
-    dict["0"]["2"]["2"] = 56.;
+    dict["0"]["1"]                = 3.5;
+    dict["0"]["2"]["1"]           = 55.;
+    dict["0"]["2"]["2"]           = 56.;
     dict["0"]["2"]["3"]["1"]["1"] = 666.;
     SECTION("Values acces by value does a copy")
     {
         auto v = dict["0"]["1"].to<double>();
-        v = 10.;
-        REQUIRE(v!=dict["0"]["1"].to<double>());
+        v      = 10.;
+        REQUIRE(v != dict["0"]["1"].to<double>());
     }
     SECTION("Values access by ref doesn't copy")
     {
-        auto &v = dict["0"]["1"].to<double>();
-        v = 10.;
-        REQUIRE(v==dict["0"]["1"].to<double>());
+        auto& v = dict["0"]["1"].to<double>();
+        v       = 10.;
+        REQUIRE(v == dict["0"]["1"].to<double>());
     }
     SECTION("Nodes access by value does copy")
     {
         auto node = dict["0"];
         node["1"] = 100;
-        REQUIRE(dict["0"]["1"].to<double>()==3.5);
-        node = dict["2"];
+        REQUIRE(dict["0"]["1"].to<double>() == 3.5);
+        node                = dict["2"];
         node["3"]["1"]["1"] = 42;
-        REQUIRE(dict["0"]["2"]["3"]["1"]["1"].to<double>()==666.);
+        REQUIRE(dict["0"]["2"]["3"]["1"]["1"].to<double>() == 666.);
     }
     SECTION("Nodes access by ref doesn't copy")
     {
-        auto &node = dict["0"];
-        node["1"] = 100;
+        auto& node               = dict["0"];
+        node["1"]                = 100;
         node["2"]["3"]["1"]["1"] = 42;
-        REQUIRE(dict["0"]["1"].to<int>()==100);
-        REQUIRE(dict["0"]["2"]["3"]["1"]["1"].to<int>()==42);
+        REQUIRE(dict["0"]["1"].to<int>() == 100);
+        REQUIRE(dict["0"]["2"]["3"]["1"]["1"].to<int>() == 42);
     }
-
 }
 
 
@@ -90,3 +90,17 @@ TEST_CASE("Contains expects true or false", "[simple cppdict::Dict<int, double,
     REQUIRE(dict["this"]["is"]["the"].contains("source"));
     REQUIRE(!dict["this"]["is"]["the"]["source"].contains("nothing"));
 }
+
+
+TEST_CASE("Dict const accessor", "[simple cppdict::Dict<int>]")
+{
+    Dict dict;
+    dict["first"]           = 3.14;
+    dict["second"]["third"] = 3;
+
+    auto const& dictRef = dict;
+
+    REQUIRE(dictRef["first"].to<double>() == 3.14);
+    REQUIRE_THROWS_WITH(dictRef["second"].to<double>(), "cppdict: to<T> invalid type");
+    REQUIRE_THROWS_WITH(dictRef["one"]["two"].to<double>(), "cppdict: invalid key: one");
+}