How to use integer constants in switch

Question

Hello!
I try:
Connection.m
#define CHANNEL_A = 0x01;
#define CHANNEL_B = 0x02;
#define CHANNEL_C = 0x03;
switch (channel){
case CHANNEL_A:
return 0;
case CHANNEL_B:
return 1;
case CHANNEL_C:
return 2;
default:
return -1;
and get: "error: syntax error before '=' token" after "case CHANNEL_A:" string
Then, I try:
Connection.h
extern const int CHANNEL_A;
extern const int CHANNEL_B;
extern const int CHANNEL_C;
Connection.m
const int CHANNEL_A = 0x01;
const int CHANNEL_B = 0x02;
const int CHANNEL_C = 0x03;
switch (channel){
case CHANNEL_A:
return 0;
case CHANNEL_B:
return 1;
case CHANNEL_C:
return 2;
default:
return -1;
and get: "case label does not reduce to an integer constant" after "case CHANNEL_A:" string

Answer 1

Or try an enum
enum CHANNELS {
CHANNEL_A = 0x01
CHANNEL_B = 0x02
CHANNEL_C = 0x03
enum CHANNELS channel;
switch(channel) {
case CHANNEL_A:
... do something ...
break;
case CHANNEL_B:
... do something ...
break;
case CHANNEL_C:
... do something ...
break;
#defines DO NOT HAVE EQUAL SIGNS! What C book are you reading?
#define CHANNEL_A = 0x01;
Associates "= 0x01" with the pre-processor macro CHANNEL_A. The pre-processor will substitute "= 0x01" everywhere it sees CHANNEL_A. So when you say
case CHANNEL_A:
the pre-processor replaces that with
case = 0x01:
and that is NOT correct case syntax, hence your compiler error.
And *const int* is not a compile time constant, or at least not one that switch/case wants to see. *const int* is a variable that you promise will not change.