If I have the following booleans
const YESTERDAY = false;
const TODAY = true;
const TOMORROW = false;
What code can I write to make sure exactly one is true?
I've tried this:
$x = self::YESTERDAY ^ self::TODAY ^ self::TOMORROW;
The problem is that with all three constants set to true then $x is true .
$x = ((int) self::YESTERDAY) + ((int) self::TODAY) + ((int) self::TOMORROW); Then if $x === 1; You've got what you need.
ReplyDeleteEDITED:
Even without type casts (int), it works well, thanks to @DaveRandom, so:
if (self::YESTERDAY + self::TODAY + self::TOMORROW == 1) {}, as for me.
The neatest way I can think of is array_sum():
ReplyDeleteif (array_sum(array(self::YESTERDAY, self::TODAY, self::TOMORROW)) == 1) {
// Do something
}
EDIT Actually, all you need to do it replace the ^ with + in your original attempt, and it achieves the same thing:
$x = self::YESTERDAY + self::TODAY + self::TOMORROW;
This turns $x into the number of TRUE values. So for a boolean output use:
$ok = self::YESTERDAY + self::TODAY + self::TOMORROW === 1;
Just as an alternative to devdRew's answer
ReplyDelete$x = array_count_values(array((int) self::YESTERDAY,(int) self::TODAY,(int) self::TOMORROW));
if (isset($x[1]) && $x[1] == 1) {
echo 'Only one TRUE';
}
You can loop over a list of your variables and break when you found a second boolean that is true:
ReplyDelete$moreThanOneTrue=false;
$oneTrue;
foreach ($BOOL_VAR_ARRAY as $bool) {
if ($bool) {
if($oneTrue) {
$moreThanOneTrue=true;
break;
}
$oneTrue=true;
}
}
Like this it's more handy when you have more than three variables.
x will return true if and only if one is true and others are false.
ReplyDelete$x = ($a && !($b || $c)) || ($b && !($a || $c)) || ($c && !($a || $b));
May be a bad code, but works.