Add better enum support in the library

README.md

@@ -178,12 +178,12 @@ While all options internally are the same type, there are several ways to add an
 
 ```cpp
 app.add_option(option_name,
-               variable_to_bind_to, // bool, int, float, vector, or string-like
+               variable_to_bind_to, // bool, int, float, vector, enum, or string-like
                help_string="",
                default=false)
 
 app.add_option_function<type>(option_name,
-               function <void(const type &value)>, // int, float, vector, or string-like
+               function <void(const type &value)>, // int, float, enum, vector, or string-like
                help_string="")
 
 app.add_complex(... // Special case: support for complex numbers

examples/enum.cpp

@@ -1,15 +1,13 @@
 #include <CLI/CLI.hpp>
 #include <map>
-#include <sstream>
 
 enum class Level : int { High, Medium, Low };
 
 int main(int argc, char **argv) {
     CLI::App app;
 
-    std::map<std::string, Level> map = {{"High", Level::High}, {"Medium", Level::Medium}, {"Low", Level::Low}};
-
     Level level;
+    std::map<std::string, Level> map = {{"High", Level::High}, {"Medium", Level::Medium}, {"Low", Level::Low}};
 
     app.add_option("-l,--level", level, "Level settings")
         ->required()

include/CLI/ConfigFwd.hpp

@@ -27,10 +27,10 @@ inline std::string ini_join(std::vector<std::string> args) {
         auto it = std::find_if(arg.begin(), arg.end(), [](char ch) { return std::isspace<char>(ch, std::locale()); });
         if(it == arg.end())
             s << arg;
-        else if(arg.find(R"(")") == std::string::npos)
-            s << R"(")" << arg << R"(")";
+        else if(arg.find_first_of('\"') == std::string::npos)
+            s << '\"' << arg << '\"';
         else
-            s << R"(')" << arg << R"(')";
+            s << '\'' << arg << '\'';
     }
 
     return s.str();

include/CLI/StringTools.hpp

@@ -46,7 +46,7 @@ inline std::vector<std::string> split(const std::string &s, char delim) {
     std::vector<std::string> elems;
     // Check to see if empty string, give consistent result
     if(s.empty())
-        elems.emplace_back("");
+        elems.emplace_back();
     else {
         std::stringstream ss;
         ss.str(s);
@@ -70,6 +70,21 @@ template <typename T> std::string join(const T &v, std::string delim = ",") {
     return s.str();
 }
 
+/// Simple function to join a string from processed elements
+template <typename T,
+          typename Callable,
+          typename = typename std::enable_if<!std::is_constructible<std::string, Callable>::value>::type>
+std::string join(const T &v, Callable func, std::string delim = ",") {
+    std::ostringstream s;
+    size_t start = 0;
+    for(const auto &i : v) {
+        if(start++ > 0)
+            s << delim;
+        s << func(i);
+    }
+    return s.str();
+}
+
 /// Join a string in reverse order
 template <typename T> std::string rjoin(const T &v, std::string delim = ",") {
     std::ostringstream s;

include/CLI/TypeTools.hpp

@@ -3,6 +3,7 @@
 // Distributed under the 3-Clause BSD License.  See accompanying
 // file LICENSE or https://github.com/CLIUtils/CLI11 for details.
 
+#include "StringTools.hpp"
 #include <exception>
 #include <memory>
 #include <string>
@@ -140,9 +141,16 @@ template <typename T, enable_if_t<is_vector<T>::value, detail::enabler> = detail
 constexpr const char *type_name() {
     return "VECTOR";
 }
+/// Print name for enumeration types
+template <typename T, enable_if_t<std::is_enum<T>::value, detail::enabler> = detail::dummy>
+constexpr const char *type_name() {
+    return "ENUM";
+}
 
+/// Print for all other types
 template <typename T,
-          enable_if_t<!std::is_floating_point<T>::value && !std::is_integral<T>::value && !is_vector<T>::value,
+          enable_if_t<!std::is_floating_point<T>::value && !std::is_integral<T>::value && !is_vector<T>::value &&
+                          !std::is_enum<T>::value,
                       detail::enabler> = detail::dummy>
 constexpr const char *type_name() {
     return "TEXT";
@@ -229,10 +237,22 @@ bool lexical_cast(std::string input, T &output) {
     return true;
 }
 
+/// enumerations
+template <typename T, enable_if_t<std::is_enum<T>::value, detail::enabler> = detail::dummy>
+bool lexical_cast(std::string input, T &output) {
+    typename std::underlying_type<T>::type val;
+    bool retval = detail::lexical_cast(input, val);
+    if(!retval) {
+        return false;
+    }
+    output = static_cast<T>(val);
+    return true;
+}
+
 /// Non-string parsable
 template <typename T,
           enable_if_t<!std::is_floating_point<T>::value && !std::is_integral<T>::value &&
-                          !std::is_assignable<T &, std::string>::value,
+                          !std::is_assignable<T &, std::string>::value && !std::is_enum<T>::value,
                       detail::enabler> = detail::dummy>
 bool lexical_cast(std::string input, T &output) {
     std::istringstream is;

tests/HelpersTest.cpp

@@ -527,6 +527,10 @@ TEST(Types, TypeName) {
 
     std::string text2_name = CLI::detail::type_name<char *>();
     EXPECT_EQ("TEXT", text2_name);
+
+    enum class test { test1, test2, test3 };
+    std::string enum_name = CLI::detail::type_name<test>();
+    EXPECT_EQ("ENUM", enum_name);
 }
 
 TEST(Types, OverflowSmall) {
@@ -617,6 +621,25 @@ TEST(Types, LexicalCastParsable) {
     EXPECT_FALSE(CLI::detail::lexical_cast(extra_input, output));
 }
 
+TEST(Types, LexicalCastEnum) {
+    enum t1 : char { v1 = 5, v3 = 7, v5 = -9 };
+
+    t1 output;
+    EXPECT_TRUE(CLI::detail::lexical_cast("-9", output));
+    EXPECT_EQ(output, v5);
+
+    EXPECT_FALSE(CLI::detail::lexical_cast("invalid", output));
+    enum class t2 : uint64_t { enum1 = 65, enum2 = 45667, enum3 = 9999999999999 };
+    t2 output2;
+    EXPECT_TRUE(CLI::detail::lexical_cast("65", output2));
+    EXPECT_EQ(output2, t2::enum1);
+
+    EXPECT_FALSE(CLI::detail::lexical_cast("invalid", output2));
+
+    EXPECT_TRUE(CLI::detail::lexical_cast("9999999999999", output2));
+    EXPECT_EQ(output2, t2::enum3);
+}
+
 TEST(FixNewLines, BasicCheck) {
     std::string input = "one\ntwo";
     std::string output = "one\n; two";