Can I use a switch case on C with multiple values? - c

Question

I'm working on that famous program that gives the date of tomorrow so I chose to use a switch to determine the months with 30 days in one case and the months with 31 days in another.
When I write case 2: it works, but when I try to write case : 4,6,9,11 it shows me an error. How can I put multiple values in one case?
switch (m) {
case 2:
do {
printf("faire entrer le jour en chiffres ");
scanf("%d", &j);
} while (j > 29 || j < 1);
if (j == 29) {
j = 1;
m = m++;
a = a;
} else {
j = j++;
m = m;
a = a;
};
break;
case (1||3||5||7||8||10||12) :
do {
printf("faire entrer le jour en chiffres \n");
scanf("%d", &j);
} while (j < 1 || j > 31);
if (j == 31) {
j = 1;
m = m++;
a = a;
} else {
j++;
m = m;
a = a;
};
break;
case 4 6 9 11 :
do {
printf("faire entrer le jour par chifre \n");
scanf("%d", &j);
} while (j < 1 && j > 30);
if (j == 30) {
j = 1;
m = m;
a = a;
} else {
j = j++;
m = m;
a = a;
};
break;
}

Answer 1

You need to use separate case labels like
case 1: case 3: case 5: case 7: case 8: case 10: case 12:
do {
//...
Or the above line can be rewritten like
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
do {
//...
Pay attention to that there is no sense to place a null statement after the closing brace as you are doing as for example
}else{
j=j++;
m=m;
a=a;
} ; break
^^^^
It is better to write
}else{
j=j++;
m=m;
a=a;
}
break

Answer 2

#Vlad from Moscow well answers how to use a switch case with multiple values.
Yet given the repetitive nature of OP's code, consider a different solution than switch.
if (m < 1 || m > 12) {
Handle_Error();
} else {
static int eom[] = { 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
do {
printf("faire entrer le jour par chifre \n");
scanf("%d",&j);
} while(j<1 || j>eom[m]);
if(j == eom[m]) {
j = 1;
m++; // add code for December to adjust `a`
} else {
j++;
}
}
Of course we still need some more changes for February and leap years.