Quote a C++ MACRO parameter

Question

I have the following template:

variable = config["variable"] ? config["variable"].as<type>() : default;

I want to create a macro to have this done for me faster, since writing this many times becomes boring. I would try something like:

#define CONFIG_PARAM(config, key, type, alt) config["key"] ? config["key"].as<type> : alt;

title = CONFIG_PARAM(root, "title", std::string, "")

It's obvious that that wouldn't work. How can I get this done?

Answer 1

To use strings inside a macro use this: #define str(s) #s This tells, that the argument has to use as a string

This is how to use ##

 #define COMMAND(NAME)  { #NAME, NAME ## _command }

 struct command
 {
   char *name;
   void (*function) (void);
 };

 // a call
 struct command commands[] =
 {
   COMMAND (quit),
   COMMAND (help),
   ...
 };

 // this expands to:
 struct command commands[] =
 {
   { "quit", quit_command },
   { "help", help_command },
   ...
 };