C: While Loop With Logical OR - c

Question

I am writing a simple text game in C where the player combats a very simple AI. Inside the main() function, there is a loop that should continue as long as the player's HP or the enemy's HP is higher than 0. See the example below.
while(grunt->hp > 0 || player->hp > 0) {
stats(player);
printf("Grunt HP: %d\n", grunt->hp);
plyMove(player, grunt);
aiMove(player, grunt);
}
if(player->hp > 0) {
printf("You won the battle!\n"); }
else {
printf("You've lost the battle!\n"); }
return 0;
Now to my understanding, this while loop should do it's thing as long as both expressions are true. If just one of them becomes false, the loop should end. However, if the enemy's HP is lower than zero, it will not break out. But if the player's HP is lower than zero, it breaks.
Every iteration of the loop is printing these values, so I can keep track of them.
Am I simply not understanding the logic of this? If you need to see any additional code, please let me know.

Answer 1

You're using a logical OR, which is true if at least one parameter is true. In other words, the truth table is this:
In | In | Out
T | T | T
T | F | T
F | T | T
F | F | F
It sounds like you want a logical AND, which is true if both parameters are true. This way, the fight continues as long as both the player and enemy have over 0 health. The operator for logical AND in C (and many other languages) is &&.
In case you're interested, here's the truth table for AND:
In | In | Out
T | T | T
T | F | F
F | T | F
F | F | F

Answer 2

While both the grunt's hp and the player's hp (true) are above 0 you want the loop to continue so you want:
while(grunt->hp > 0 && player->hp > 0)
If either the grunt's hp or the player's hp goes below 0 the condition above will be false and you will exit the loop.

Answer 3

If in your head you were thinking "I want to end the game when the player's HP or the enemy's HP is below or equal to zero", the right while condition would be:
while(!(grunt->hp <= 0 || player->hp <= 0))
With the logical inverse operator !
Recall: !(A || B) == !A && !B so other guys answer is strictly equivalent.

Answer 4

Sometimes an abstraction can make things easier to grasp.
Consider if you had:
#define Alive(who) ((who)->hp > 0)
then you could write:
while (Alive(grunt) && Alive(player)) {
…
}