const_c_vs_cpp.md

Stackoverflow topics about const vs #define in C/C++:

• http://stackoverflow.com/questions/1674032/static-const-vs-define-vs-enum

• http://stackoverflow.com/questions/1637332/static-const-vs-define

Below an example of switch statement used with const variables in C and C++.

C:

dc@dc:/tmp$ cat test.c && gcc test.c
#include <stdio.h>

const int a1 = 1;
const int a2 = 2;

int main(int argc, char* argv[]) {
    switch(argc) {
        case 0:
            puts("ZERO");
            break;
        case a1:
            puts("1");
            break;
        case a2:
            puts("2");
            break;
    }
}
test.c: In function ‘main’:
test.c:11:9: error: case label does not reduce to an integer constant
         case a1:
         ^
test.c:14:9: error: case label does not reduce to an integer constant
         case a2:
         ^

C++:

dc@dc:/tmp$ cat test.cpp && g++ test.cpp && ./a.out
#include <stdio.h>

const int a1 = 1;
const int a2 = 2;

int main(int argc, char* argv[]) {
    switch(argc) {
        case 0:
            puts("ZERO");
            break;
        case a1:
            puts("1");
            break;
        case a2:
            puts("2");
            break;
    }
}
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dc@dc:/tmp$