I want to know why the scripting language doesn't add check key/mouse release functions?
Just like these things:
key_w_release, key_a_release, mouse_left_release, mouse_right_release......etc.
With these functions, scripting will be more handy, right?

We don't want to implement trivial functions that can easily implemented by yourself. For this just evaluate the corresponding key or mouse values (mouse_left, mouse_right etc).

I don't think it is trivial functions...
Without checking release functions, I should write like this:

var key_w_release=off;
action PlayerAction()
{
while(1)
{
if(key_w && key_w_release==off)
{key_w_release=on;}
if(!key_w && key_w_release)
{
//other code
key_w_release=off;
}
wait(1);
}
}

I think this way is inconvenient.
with the release functions, I should only do this:
action PlayerAction()
{
while(1)
{
if(key_w_release)
{
//other code
}
wait(1);
}
}
Isn't this more concise?
Or just invent a general function to check if a key is released.
Such as check_key_release(key_w), return true or false.
Same as the mouse, check_mouse_release(mouse_left).

you can of course implement a general function to check this. store all your keys you want to survive with their scancodes in an array (forget about the unused space this time, you could also use a dynamic list or something). then, per frame, work with key_pressed to store wether a key has been released this frame (you had the correct code in your last sample). write a small function which returns your release state. approximately 20 lines of code.

joey.