Choosing enum element using “…” [duplicate]

问题

This question already has answers here:

What is “…” in switch-case in C code (4 answers)

Closed 4 years ago.

Is '...' symbol is a c language keyword?

The code:

#include <stdio.h>

typedef enum {
    A=0,B,C,D,E,F,G,H,I,J,K,M
} alpha;


int main(int argc, char const *argv[])
{


    alpha table = C;

    switch (table)
    {
        case A ... D:
        /* I have never seen "..." grammar in textbook */
            printf("Oh my god\n");
            break;
        default:
            printf("default\n");
            break;
    }
    return 0;
}

Is ... allowed in C for range?

回答1:

It's not standard C, but a GCC extension:

You can specify a range of consecutive values in a single case label, like this:

case low ... high:

This has the same effect as the proper number of individual case labels, one for each integer value from low to high, inclusive.

More in GCC extension: Case ranges

回答2:

This is called Case Ranges. And no, this is not a standard C feature.

It is implemented as gcc extension. This is just another way to use fall-through case statement.

来源：https://stackoverflow.com/questions/37318196/choosing-enum-element-using