flow control?

[lincore]

Hi there,

I know this question must have been asked a zillion times, but the search function didn't give me any useful advice on how to do this. So I'm asking AGAIN:

Is there a way to execute a loop (repeat, while, for etc.) inside an event? I need that for slope detection in a platformer since I want to avoid using too many detectors. I wrote the following algorithm in c/pseudo code to illustrate what I am planning to do:

Slope detection:

I am using fast loops to move the player one pixel at a time.
When the player overlaps with the background we have to check
if there is a free position available that is no more than X
pixels (three, for instance) above the current position,
which _should_ be done with a loop:

Example:
###
####            # = Background
#####           P = Player
#####  P
#######P
##################################
Now, when the player moves one pixel to the left, the
following code will be executed:

------------------------------------------------------

    if (player overlaps with obstacle)
    {
      if (player is moving left) 
      {     
        int x = player.leftX;
        int backwards = +1;
      }
      elseif (player is moving right)
      { 
        int x = player.rightx;
        int backwards = -1;
      }
      
      for (int i = 1; i <= 3; ++i) 
      // repeat the following block three times and increase i by 1 each cycle:
      {
        if (getObjectAtPosition(x, player.lowerY + i) is not an obstacle)
        {
          player.Y += i; // slope found, move player up
          return true;
        }      
      } //for
      
      // no slope, player goes back where he came from
      player.x += backwards; 
      return false;
    } //if
  } //if

Can this be done with mmf2? I don't care if it's dirty, as long as it's reliable and can be used for players and enemies as well. If you have any good ideas about this, please let me know.

Thanks in advance,
lincore

[DavidN]

Yes, the Fastloop feature is what you should use here. When a loop is started, the events with the condition "On loop 'xxx'" as their first condition are executed the number of times you specify, before the event list continues and the frame is next redrawn.

For your example, you would start the loop (let's call it PushUp) three times, in which you would have:

On loop "PushUp"
+ The pixel at X, Y Bottom from Player is not an obstacle
-> Move player up
-> Stop loop "PushUp"

It's probably easier, though, to restructure the FOR loop you have there so that it's a function in itself, as this is more easily translatable into event form.

[lincore]

Thank you David for your advice (and that tutorial on custom platform movement). My fast loop powered slope detection kinda works, though there are some odd "stuck in the wall" bugs. Nothing too serious, I assume.

Looks like a good time to take a break.
Goodnight,
lincore