Added support for integer type in choices

README.md

@@ -1060,13 +1060,7 @@ argparse::ArgumentParser program("test");
 
 program.add_argument("input")
   .default_value(std::string{"baz"})
-  .action([](const std::string& value) {
-    static const std::vector<std::string> choices = { "foo", "bar", "baz" };
-    if (std::find(choices.begin(), choices.end(), value) != choices.end()) {
-      return value;
-    }
-    return std::string{ "baz" };
-  });
+  .choices("foo", "bar", "baz");
 
 try {
   program.parse_args(argc, argv);
@@ -1083,7 +1077,34 @@ std::cout << input << std::endl;
 
 ```console
 foo@bar:/home/dev/$ ./main fex
-baz
+Invalid argument "fex" - allowed options: {foo, bar, baz}
+```
+
+Using choices also works in integer types, e.g.,
+
+```cpp
+argparse::ArgumentParser program("test");
+
+program.add_argument("input")
+  .default_value(0)
+  .choices(0, 1, 2, 3, 4, 5);
+
+try {
+  program.parse_args(argc, argv);
+}
+catch (const std::exception& err) {
+  std::cerr << err.what() << std::endl;
+  std::cerr << program;
+  std::exit(1);
+}
+
+auto input = program.get("input");
+std::cout << input << std::endl;
+```
+
+```console
+foo@bar:/home/dev/$ ./main 6
+Invalid argument "6" - allowed options: {0, 1, 2, 3, 4, 5}
 ```
 
 ## Using `option=value` syntax

include/argparse/argparse.hpp

@@ -350,6 +350,17 @@ std::string join(StrIt first, StrIt last, const std::string &separator) {
   return value.str();
 }
 
+template <typename T>
+struct can_invoke_to_string {
+  template <typename U>
+  static auto test(int) -> decltype(std::to_string(std::declval<U>()), std::true_type{});
+  
+  template <typename U>
+  static auto test(...) -> std::false_type;
+  
+  static constexpr bool value = decltype(test<T>(0))::value;
+};
+
 } // namespace details
 
 enum class nargs_pattern { optional, any, at_least_one };
@@ -408,6 +419,14 @@ public:
 
   template <typename T> Argument &default_value(T &&value) {
     m_default_value_repr = details::repr(value);
+
+    if constexpr (std::is_convertible_v<T, std::string_view>) {
+      m_default_value_str = std::string{std::string_view{value}};
+    }
+    else if constexpr (details::can_invoke_to_string<T>::value) {
+      m_default_value_str = std::to_string(value);
+    }
+
     m_default_value = std::forward<T>(value);
     return *this;
   }
@@ -525,12 +544,19 @@ public:
     return nargs(nargs_pattern::any);
   }
 
-  void add_choice(const std::string &choice) {
+  template <typename T>
+  void add_choice(T&& choice) {
+    static_assert(std::is_convertible_v<T, std::string_view> || details::can_invoke_to_string<T>::value, "Choice is not convertible to string_type");
     if (!m_choices.has_value()) {
-      /// create it
       m_choices = std::vector<std::string>{};
     }
-    m_choices.value().push_back(choice);
+
+    if constexpr (std::is_convertible_v<T, std::string_view>) {
+      m_choices.value().push_back(std::string{std::string_view{std::forward<T>(choice)}});
+    }
+    else if constexpr (details::can_invoke_to_string<T>::value) {
+      m_choices.value().push_back(std::to_string(std::forward<T>(choice)));
+    }
   }
 
   Argument &choices() {
@@ -540,18 +566,10 @@ public:
     return *this;
   }
 
-  template <typename... T>
-  Argument &choices(const std::string &first, T &...rest) {
-    add_choice(first);
-    choices(rest...);
-
-    return *this;
-  }
-
-  template <typename... T> Argument &choices(const char *first, T &...rest) {
-    add_choice(first);
-    choices(rest...);
-
+  template <typename T, typename... U>
+  Argument &choices(T&& first, U&&...rest) {
+    add_choice(std::forward<T>(first));
+    choices(std::forward<U>(rest)...);
     return *this;
   }
 
@@ -560,7 +578,7 @@ public:
     const auto &choices = m_choices.value();
 
     if (m_default_value.has_value()) {
-      if (std::find(choices.begin(), choices.end(), m_default_value_repr) ==
+      if (std::find(choices.begin(), choices.end(), m_default_value_str) ==
           choices.end()) {
         // provided arg not in list of allowed choices
         // report error
@@ -1152,6 +1170,7 @@ private:
   std::string m_metavar;
   std::any m_default_value;
   std::string m_default_value_repr;
+  std::optional<std::string> m_default_value_str; // used for checking default_value against choices
   std::any m_implicit_value;
   std::optional<std::vector<std::string>> m_choices{std::nullopt};
   using valued_action = std::function<std::any(const std::string &)>;

test/test_choices.cpp

@@ -68,3 +68,24 @@ TEST_CASE("Parse multiple arguments one of which is not in the fixed number of "
       "Invalid argument \"green2\" - allowed options: {red, green, blue}",
       std::runtime_error);
 }
+
+TEST_CASE(
+    "Parse multiple arguments that are in the fixed number of allowed INTEGER choices" *
+    test_suite("choices")) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("indices").nargs(2).choices(1, 2, 3, 4, 5);
+
+  program.parse_args({"test", "1", "2"});
+}
+
+TEST_CASE(
+    "Parse multiple arguments that are not in fixed number of allowed INTEGER choices" *
+    test_suite("choices")) {
+  argparse::ArgumentParser program("test");
+  program.add_argument("indices").nargs(2).choices(1, 2, 3, 4, 5);
+
+  REQUIRE_THROWS_WITH_AS(
+      program.parse_args({"test", "6", "7"}),
+      "Invalid argument \"6\" - allowed options: {1, 2, 3, 4, 5}",
+      std::runtime_error);
+}