Switch with "mask" variable

Question

The variable:

$mask = A | B | C;

And I can use switch to test each constant like this:

switch(true){
  case $mask & A:
   ...
  case $mask & B:
   ...
  case $mask & C:
   ...
}

I was wondering if it's possible to have a nicer switch, like:

switch($mask){
  case A:
   ...
  case B:
   ...
  case C:
   ...
}

I believe I need to modify the variable somehow with the weird ~ operator thing. but how?

plus with a switch it will only match one condition... a mask usually defines multiple conditions. — Orangepill, Jul 22 '13 at 18:49
actually it will work but the switch will dump after the first match. — Orangepill, Jul 22 '13 at 18:54
Switch is a bad choice to implement bitmask computing, unless there is cascading dependency on each one. See http://stackoverflow.com/a/5319489/258674 how it should be done. — dev-null-dweller, Jul 22 '13 at 18:57

score 1 · Accepted Answer · answered Jul 22 '13 at 18:57

It is possible to structure a switch as you stated

<?php

define("A", 1);
define("B", 2);
define("C", 4);


$mask = B | C;

switch(true){
  case $mask & A:
    echo "A";
    break;
  case $mask & B:
    echo "B";
    break;
  case $mask & C:
    echo "C";
    break;
}
?>

But the problem is a switch will only trigger the first matching condition. So the above code with $mask = B | C; will only echo B when you probably want it to echo BC

So in short if you want the behavior to be that it executes only the first matching condition then you can use this otherwise you will have to do a series of ifs.

what if you remove all the 'break' directives, wont it then flow through all the cases and execute where it matches ? — Nicholas Hamilton, Dec 09 '22 at 05:34

Switch with "mask" variable

1 Answers1