[hogliux]

Yes, in a way you are right: the compiler really does boil it down to global variables. However, `semi::static_map` gives you some additional features, which may be useful for a lot of situations

1) `semi::static_map` gives you the optional run-time look-up with the same API (`semi::static_map::get`). Looking up a global variable with a runtime key isn't straight-forward. This makes it particularly nice to use an API where a function might take either a compile-time or run-time key. I'm thinking a Font API with a `getFont` method, for example. The way you use the method is the same regardless if you are using a compile-time key or not.

2) `semi::static_map` also gives you control over the lifetime of the objects. For example, it's easy to delete all the values in the map at once. Again, this is not straight-forward to do with a bunch of globals.

3) the keys are also values themselves and it's straight-forward to evaluate them at run-time. Printing the name of a global variable, for example, requires all sorts of hackery.

4) you do not need to know all your keys in advance. Simply using getFont with a unique constexpr key will create a new global variable.

Edit: added point (4)

[jstimpfle]

Re: 3), here's a clean and technically humble way that I typically use.

    enum {
        KEY_FOO,
        KEY_BAR,
        KEY_BLAH,
        NUM_KEYS,
    };

    struct KeyInfo {
        const char *name;
        int info1;
        float info2;
    };

    const static struct KeyInfo keyInfo[NUM_KEYS] = {
    #define MAKE(x, y, z) [x] = { #x, y, z }
        MAKE( KEY_FOO,   1,   1.0 ),
        MAKE( KEY_BAR,   7,   3.5 ),
        MAKE( KEY_BLAH, 42, 127.2 ),
    #undef MAKE
    };

    void print_key(int key)
    {
        printf("%d's name is %s\n", key, keyInfo[key].name);
    }

It's both low-tech and maintainable. It compiles super quick. If one doesn't like that one has to type KEY_FOO twice (in the enum and in the array definition), one can use X-macros or code generation. But personally I don't care.

[hogliux]

Yes, that's a nice approach. However, this approach requires you to list all your keys in advance (in the enum).

The `semi::static_map` does not require this.This is especially useful if you are writing library code: imagine you are programming a `getFont` method - you don't know with which constexpr keys your method will be called, so there is no way for you to list all these keys in an enum.

[kazinator]

If you don't like pointlessly repeating occurrences of identifiers, you should hardly be favoring C++.

   class foo {
   public:
     foo();
     ~foo();
   };
 
   foo::foo() { }

   foo::~foo() { }

Ad nauseum.

Oh, but C++ can eliminate redundancy in this one cool case I'm thinking of!

[IshKebab]

C++ doesn't support designated initialisers.

[petters]

Thanks for this clarification! I agree it can be useful.