Squashed 'libs/cli11/' content from commit dcbcb47

git-subtree-dir: libs/cli11
git-subtree-split: dcbcb4721dda5dab0a56d9faaaee50e6a30f7758

book/code/flags.cpp

@@ -0,0 +1,36 @@
+#include "CLI/CLI.hpp"
+#include <iostream>
+
+int main(int argc, char **argv) {
+    using std::cout;
+    using std::endl;
+    CLI::App app{"Flag example program"};
+
+    /// [define]
+    bool flag_bool;
+    app.add_flag("--bool,-b", flag_bool, "This is a bool flag");
+
+    int flag_int;
+    app.add_flag("-i,--int", flag_int, "This is an int flag");
+
+    CLI::Option *flag_plain = app.add_flag("--plain,-p", "This is a plain flag");
+    /// [define]
+
+    /// [parser]
+    try {
+        app.parse(argc, argv);
+    } catch(const CLI::ParseError &e) {
+        return app.exit(e);
+    }
+    /// [parser]
+
+    /// [usage]
+    cout << "The flags program" << endl;
+    if(flag_bool)
+        cout << "Bool flag passed" << endl;
+    if(flag_int > 0)
+        cout << "Flag int: " << flag_int << endl;
+    if(*flag_plain)
+        cout << "Flag plain: " << flag_plain->count() << endl;
+    /// [usage]
+}