Generic Coding Question

[seveianrex]

Okay, admittedly I'm a self taught programmer and I never quite understood binary operators.

In working with the "CLASSES" column for AA's I was able to get a grasp on the binary 'AND' (&) operator, and I understand how bitshifting (1 << value) works.


I was curious though... I've seen some very elegant looking code before in terms of something like the following:

switch (GetAA(aaNumberOne) | GetAA(aaNumberTwo))
{
//blah
}

which would utilize the non-zero value.

would the above code work? if aaNum1 returned 0 and aaNum2 returned 3, for example, would it switch (3) ?

just seems a lot more elegant than doing two switches that do the same thing. i realize i could use an integer variable too, but that gets clunky lookin'.

[Sildorei]

No, it wouldn't work because in a switch you'll only use a code like following :

switch(myvar)

You can't use a binary operator in a switch ( i think).

[spoon]

Actually it should work because bitwise operations are expressions that return an integral type. An expression doesn't have to be just a variable.

VS2005 switch definition

And our quick test proves it:

#include <iostream>
using namespace std;

int main() {
	int x = 1;
	int y = 5;
	
	switch( x | y ){
		case 0: printf("0"); break;
		case 1: printf("1"); break;
		case 2: printf("2"); break;
		case 3: printf("3"); break;
		case 4: printf("4"); break;
		case 5: printf("5"); break;
		case 6: printf("6"); break;
		case 7: printf("7"); break;
		default: printf("other"); break;
	}
}

5

[Derision]

You're fine if one of the two operands is always zero, but you may get strange results if both are non-zero, e.g. 1 | 3 = 3, 1 | 4 = 5.

[spoon]

I would bet he is asking because of the duplicate AAs where one would always be 0.

However, I don't think this is a "elegant" solution, but a clever one. Clever meaning buggy and hard to maintain. At this level of abstraction, we are dealing with int32s and not bits or bitmasks. You could do something like:

int32 aaValue = ( GetAA(aaNumberOne) > GetAA(aaNumberTwo) )  ? GetAA(aaNumberOne) : GetAA(aaNumberTwo);

case(aaValue) {
... snip ...

if you wanted to be clever, but still maintain the proper level of abstraction. However I would write the extra couple lines and maybe add a comment just to let the maintainer know whats going on.

I tend to follow the KISS principle (Keep It Simple Stupid)

[spoon]

Originally Posted by spoon

case(aaValue) {

switch(aaValue) {