Enum issue when converting from C++ to C

Question

I am in the process of changing my C++ code into C code because I find myself gravitating toward more purely functional programs and am not really using any of the C++ features. The speedy compiling is also a plus.

I am having trouble with this particular bit in my header:

void gameLoop();
void doStuff();

enum GameState
{
    MENU, PLAY, EXIT
};

GameState gameState;

which I want to use for functions like this in my source:

void gameLoop() 
{
    while (gameState != GameState::EXIT)
    {
        doStuff();

    }
}

In C and you cannot use ::; you need to use while (gameState != EXIT) (this should also work in C++ and that's why in C++ you should use enum class. — fabian
– fabian, Commented Jun 18, 2021 at 16:44
Please don't modify your question in a way that makes answers nonsensical. You removed the GameState::EXIT from the question and now your switch statement is malformed. — Mark Ransom
– Mark Ransom, Commented Jun 18, 2021 at 17:30
Sorry about that. Fixed to show both the original and modified code in unambiguous way — Jeffrey
– Jeffrey, Commented Jun 18, 2021 at 17:41
If you want more purely functional programming, C++ is to me a far better choice than C because it has lambda functions, implementing closures. Having true closures in pure C seems to be difficult and very verbose. — prapin
– prapin, Commented Jun 19, 2021 at 6:53

Adrian Mole · Accepted Answer · 2021-06-18 17:09:22Z

4

As pointed out in the comments, you can't use the scope-resolution operator (::) in C (there is no such operator). Further, if you want to use GameState as a variable type (as in your declaration, GameState gameState;) then you will need to explicitly define it as a type, using the typedef keyword.

Here's a version of the code you posted translated to C (note also the explicit void argument list declarations):

void gameLoop(void);
void doStuff(void);

typedef enum {
    MENU, PLAY, EXIT
} GameState;

GameState gameState;

void gameLoop(void)
{
    while (gameState != EXIT) {
        doStuff();
    }
}

As an improvement, you may like to add suitable 'prefixes' to the enum values, to avoid possible clashes with similar IDs declared elsewhere:

typedef enum {
    gsMENU, gsPLAY, gsEXIT
} GameState;

edited Jun 18, 2021 at 17:09

answered Jun 18, 2021 at 17:03

Adrian Mole

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1 Comment

Neil Over a year ago

enum GameState {...} gameState; saves having to pollute the typedef namespace, which gets pretty crowded. See namespaces in C.

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