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If the operator for multiple scenarios

I am struggling to complete this if statement. There must be an easier way to go through all the combinations, because it might not be good practice.

if( one == true && two == true && three == true ...)
else if( one != true && two == true && three == true ...)

I wonder if I want to go through all the combinations, is there any other way to do this rather than duplicating the expression?

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5 answers


One way is to convert the values one

, two

both three

to one int

with the correct bits set and using instructions switch

for binary masks, for example:

int combined=0;
// Construct a binary representation using your Boolean values as bits:
// Value of one goes to bit zero
if (one) combined   |= (1 << 0);
// Value of one goes to bit one
if (two) combined   |= (1 << 1);
// Value of three goes to bit two
if (three) combined |= (1 << 2);
switch (combined) {
case 0: // All false
    break;
case 1: // one is true, other are all false
    break;
...
case 7: // All true
    break;
}

All eight combinations are now encoded as integer values:



int    three two one
_--    ----- --- ---
0    -    0   0   0 
1    -    0   0   1 
2    -    0   1   0 
3    -    0   1   1 
4    -    1   0   0 
5    -    1   0   1 
6    -    1   1   0 
7    -    1   1   1

It goes without saying that you need to heavily comment on such code for readers of your code who have not memorized the binary representations of small numbers.

+19


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You can do something like:

int i = (one ? 1 : 0) | (two ? 2 : 0) | (three ? 4 : 0);

switch(i)
{
     case 0:
         // ...
     case 1:
         // ...
     case 7:
         // ...
}


It will be very fast - it will be a direct branch ( opcodeswitch

) and expressions will only be evaluated once.

+18


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You don't need one != true

the second line as you have already eliminated the case where everything is correct. You can simplify this usage:

if (one && two && three) {
}
else if (one && two) { 
} 
else if (two && three) {
}
else if (one && three) {
}
else if (one) {
}
else if (two) {
}
else if (three) {
}
else
{
  // none true
}
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Perhaps you could try this:

if (one && two && three)
{
    // Do something
}
else if(one && two && three ...)
{
    // Do Something else
}

to test the use of the false operator '!':

if (!one && two ...)
0


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The best way to do this is to have each of these elements declared as bool. This way you can delete all lines == ?

and have something like this:

bool one = true; // Random decision to call it true, just for testing
bool two = false;
bool three = true;

if(one && two && three)
    // Do something
else if(!one && two && three)
    // Do something else.
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