If you only want to know if a key is up or down, then yes, you could just use boolean.

case ALLEGRO_KEY_DOWN: key[event.keyboard.keycode] = true; break;
case ALLEGRO_KEY_UP: key[event.keyboard.keycode] = false; break;

The Vivace code, however, tracks key presses not only ups or downs.

What happens when a key is pressed and released before the next set of logic instructions? It would not recognize that a key was pressed at all.

Once, logic is done, this code is processed:

for(int i = 0; i < ALLEGRO_KEY_MAX; i++)
    key[i] &= KEY_SEEN;

It resets the "released" state of all keys, but keeps the "seen" state. Meaning any key that is still being pressed will remain seen.

----

Maybe it's me, but I don't understand what you are asking.

1 is the same thing as 00000001

-----

This statement checks to see if the key is pressed or was pressed since last logic check.

This question is where I'm confused on what you are asking.

The code toggles the 1st and 2nd bits. It's true if any bit is set.

zero = false
nonzero = true

This is not a good explanation of bitwise operations.

First you need to know what each bitwise operator does.

&      0     1
0      0     0
1      0     1

|      0     1
0      0     1
1      1     1

Bitwise AND only returns a 1 bit if both arguments are 1s.
Bitwise OR only returns a 1 bit if either argument is a 1.
Bitwise NOT returns a 0 if 1 or 1 if 0
Bitwise XOR returns a 1 if both bits are different and 0 otherwise.

I don't know what 'seen' is supposed to mean, but I guess it is tracking key presses and not just key down.

My input library does all this for you and more.

For example, key presses and releases are tracked automatically, and all you have to do is check a boolean array.

if (input_key_released(EAGLE_KEY_X)) {
   /// User let go of x key
}
if (input_key_press(EAGLE_KEY_Y) {
   /// user just pressed y
}
if (input_key_held(EAGLE_KEY_LCTRL) {
   /// L CTRL is held
}
// etc...

I accomplish the same thing by using a dual array of keys.

if (!oldkey[ALLEGRO_KEY_SPACE] && key[ALLEGRO_KEY_SPACE]) {
   /// space key was just pressed
}

Edgar,

Being a bitwise novice, in my first attempt to follow the bit changes in the tutorial I came up with different results. The code worked so I knew I was misunderstanding it.

I thought the if statements were doing multiple things in one line of code. Capturing the keystroke and then evaluating it some how. Looking back I see it was a crazy thought. No matter how you formulate it whatever is between a set of array [brackets] is just an index of the array.

Daniel,

I think I'm understanding the AND & OR part a little better. I was just getting confused on when the bits were actually changing.

In my opinion the tutorials are pretty good. I think they "take the long way around" to allow the reader to see how things function. Normally I don't work so hard to understand every little thing. I copy/paste code then learn from the altering to fit my code. I allow for the fact there are things going on behind the scenes I'll never understand.

One last question on the subject. Are bitwise operators worth the effort? I can see the benefit if you are coding the next Elder Scrolls but I'm not seeing it with small console type games or something the average programmer would do.

From a novice stand point, the benefit is for program run speed and minimizing memory usage. With today's machines is that as big a concern as it originally was?

Just curious.

They have their uses, but not for everything.

For instance, Allegro uses them for setting flag options.

I use either bitwise operations and/or bit fields to simplify things and decrease overhead.

If forget what game it was, but years ago I made a map system. I wanted a more precise collision system then checking if the whole tile was blocked or not. I broke the tile down into smaller squares chunks. A segment was blocked if that bit was set or not. In my map editor, I could set/unset the entire tile or individual chunks.

Yes! That's what we do. Regular programming is boring. We try a tweak it and make it harder.

Something like tictactoe. You could make a simple int grid[9], but why?

The code I posted before was just a concept I've been working in my head. I planned to add another video to my library making TicTacToe. I SHOULD make it simple and use the brute force approach. However, I don't like simple.

In school for by Bachelor's Degree, I took an AI class. In it we had to write a tictactoe game in Java. In it, we also had to implement some simple AI using the minmax algorithm. Not particular hard to do.

need a function to evaluate a grid.
return 10 is X wins
return -10 if O wins
return 0 if no wins

When it was the computers turn, it looked at all available moves for O. For each move, evaluate the grid. Pick the minimum values (might have multiple minimums). If the grid value was -10, it won. It the minimum grid value was zero, then it would do another layer deeper. This time it would calculate all possible moves for X and find the maximum value. If any grid values were again zero, then go another layer deeper.

Repeat until win/lose or no more moves

To the point: each layer and iteration requires a copy of the previous. While an array of 9 integers is not much. 1 integer is better.

As you say Dizzy I often take a trial-and-error approach which has its pitfalls. When I went to college the languages offered were Cobal & Fortran. I even took two semesters of IBM’s RPG. I don’t recall any PC style languages like C being offered. From what I could tell most were mainframe based. The learning I’ve done has been on my own with no real demand for my programs. Like a self-taught musician, I’m sure I’ve developed bad habits that are now crippling when trying to expand how I think / pseudo code programs.

Daniel, I’ve never had the luxury to mess with AIs. Sounds like it would be cool. I do try to get the computer to generate objects automatically / mathematically when I can figure out how to. However, there are times (TicTacToe) where I just write in the possible conditions and have the computer compare. Example, my most recent game was a board game with a maze aspect. I tried for days to figure out how to get the computer to generate the maze automatically. This would allow it to be more random. I was close I could feel it. Eventually I gave up and created 20 maps within the code. With the 20 maps and 81 potential starting points the chance of duplication seems minimal. Again, manually doing something that could be done automatically. But I digress .