Validating an enumeration on input using switch and a warning

gistfile1.m

//So you have an enumeration that counts up to some value.
enum {
	A = 1,
	B, C, D, E, F, G, H, I,
	J
};

//You may be reading this enum from an input file. You'd like to check whether you have a valid value.
//One way would be to have a count value:
enum {
	A = 1,
	B, C, D, E, F, G, H, I,
	J,
	numLetters
};

unsigned value = /*input*/;
if (value < numLetters)
    valid = true;
else
    valid = false;

//But, as @steve_holt points out, this breaks the “switch has unhandled cases” warning: any switch that handles this enum now needs to handle the numLetters case, which is not a valid case itself.
// https://twitter.com/steve_holt/status/405045512786554880

//What you can do instead is use that very same warning:

valid = false;
switch (value):
    case A:
    case B:
    case C:
    case D:
    case E:
    case F:
    case G:
    case H:
    case I:
    case J:
        valid = true;
}

//Long way around, but it does the job without breaking the warning.