relative values, types check

src/data/dynamic.cpp

@@ -242,6 +242,20 @@ size_t Map::size() const {
     return values.size();
 }
 
+static const std::string TYPE_NAMES[] {
+    "none",
+    "map",
+    "list",
+    "string",
+    "number",
+    "bool",
+    "integer",
+};
+
+const std::string& dynamic::type_name(const Value& value) {
+    return TYPE_NAMES[value.index()];
+}
+
 List_sptr dynamic::create_list(std::initializer_list<Value> values) {
     return std::make_shared<List>(values);
 }
@@ -249,3 +263,19 @@ List_sptr dynamic::create_list(std::initializer_list<Value> values) {
 Map_sptr dynamic::create_map(std::initializer_list<std::pair<const std::string, Value>> entries) {
     return std::make_shared<Map>(entries);
 }
+
+number_t dynamic::get_number(const Value& value) {
+    if (auto num = std::get_if<number_t>(&value)) {
+        return *num;
+    } else if (auto num = std::get_if<integer_t>(&value)) {
+        return *num;
+    }
+    throw std::runtime_error("cannot cast "+type_name(value)+" to number");
+}
+
+integer_t dynamic::get_integer(const Value& value) {
+    if (auto num = std::get_if<integer_t>(&value)) {
+        return *num;
+    }
+    throw std::runtime_error("cannot cast "+type_name(value)+" to integer");
+}

src/data/dynamic.hpp

@@ -35,8 +35,16 @@ namespace dynamic {
         integer_t
     >;
 
+    const std::string& type_name(const Value& value);
     List_sptr create_list(std::initializer_list<Value> values={});
     Map_sptr create_map(std::initializer_list<std::pair<const std::string, Value>> entries={});
+    number_t get_number(const Value& value);
+    integer_t get_integer(const Value& value);
+    
+    inline bool is_numeric(const Value& value) {
+        return std::holds_alternative<number_t>(value) ||
+               std::holds_alternative<integer_t>(value);
+    }
 
     class List {
     public: