This is just a very small C-Script contribution. I needed a code that could query if a key was pressed ONCE (So holding the key won't repeat the respective action).
For instance, I needed the player to press SPACEBAR once for every Jump of the character, because Holding the SPACEBAR should be used to Grab over ledges after jumping. With the normal key_pressed(), the jump would be repeated all the time while SPACE is held.
Also, commands like "NEXT_WEAPON", "PREVIOUS WEAPON", and certain attacks with the mouse button should not be quickly repeated: they should work only once for each time the key is pressed.

Code:

---

define KEY_NORMAL,0;
define KEY_ONCE,1; 

var is_key_hold[300];

function keypressed (keycode, keymode)
{	
	if (key_pressed(keycode))
	{
		if (is_key_hold[keycode])
		{
			if (keymode == KEY_ONCE)
			{
				return (off); //press once mode
			}
			return (on); //normal mode
		}
		else
		{
			is_key_hold[keycode] = on;
			return (on); //key ON in both normal and press_once modes
		}	
	}
	else
	{
		is_key_hold[keycode]=off;
		return (off);
	}
}

---

To use it instead of key_pressed, use:

if (keypressed(scancode,KEY_NORMAL) ) {...}

To query if a key has been pressed one time (not being held), use:

if (keypressed(scancode,KEY_ONCE) ) {...}


It's important to completely replace key_pressed by this function, at least for the needed non-repeating keys, because the keypressed() function automatically sets the key HOLD flags on and off in an array.

Thanks for your comments!

you could just have used

on_space = grab_function;

thanks for the tip

My project is a bit complex, although. It reads and saves key labels and definitions from files in portuguese, english or spanish, and uses complex key commands. Some weapons are auto-repeat, others not, others depend on holding a key like a bow and arrow... So I prefer to have things under control this way.

Of course it's up to every user. If you like this quick snippet, you can use at will.