Syntax problem, how is then missing in this statement

[chaucer345]

Hi guys, I get an error message when I try to compile the code below. The compiler claims there is an if statement missing a then, even though the then is present. I came in from java so I'm still new to this semi-english syntax.

Code: Select all

if the top of image pUp OR the top of image pDown OR the top of image pLeft OR the top of image pRight and Rectangle1 OR Rectangle2 OR Rectangle3 OR Rectangle4 OR Rectangle5 OR Rectangle6 OR Rectangle7 OR Rectangle8 OR Rectangle9 OR Rectangle10 intersect then
      put false into intersectst
   else 
      put true into intersectst
   end if

I can't figure out what's wrong, do you have any advice?

[DavJans]

Looks like the format is wrong

try this

if intersect( <object1> , <object2> ) then

[dunbarx]

Hi.

What is the story with that "intersect" thingie at the end of that outrageous first line?

Anyway, that is your culprit. Sometimes the engine complains, like a petulant child, and you are not sure whether it is hungry or wet. The best way to figure these things out is to comment from right to left, re-inserting a "then" as you go, until you get no error after compiling.

Craig Newman

[chaucer345]

Hi.

What is the story with that "intersect" thingie at the end of that outrageous first line?

Anyway, that is your culprit. Sometimes the engine complains, like a petulant child, and you are not sure whether it is hungry or wet. The best way to figure these things out is to comment from right to left, re-inserting a "then" as you go, until you get no error after compiling.

Craig Newman

Thank you for the advice!

That was me miss-understanding the syntax... and yeah, I know that statement is kind of silly. It's basically me checking for collisions of the player sprite with all of the rectangles on the screen. The theoretically working version?

Code: Select all

 if  intersect ((the top of image pUp OR the top of image pDown OR the top of image pLeft OR the top of image pRight), (Rectangle1 OR Rectangle2 OR Rectangle3 OR Rectangle4 OR Rectangle5 OR Rectangle6 OR Rectangle7 OR Rectangle8 OR Rectangle9 OR Rectangle10)) then
      put false into intersectst
   else 
      put true into intersectst
   end if

On a side note if you know a more efficient way to check for intersections like this I'd be very glad to hear it.

Edit: That code appears to throw the following error:
card id 1002: execution error at line n/a (Chunk: error in object expression) near "false", char 1

[Simon]

Hi chaucer345,
I think it would be best to start here;

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if  intersect (the top of image pUp,Rectangle1) then

if that works for you then add the rest 1 by 1 testing each time.

So, you have 4 images colliding with 10 rectangles.
Do you need to use "top"? Wouldn't any intersect work for you? Yes, yes I know it's the top of the image because this is a vertical slider. but any intersect would do wouldn't it?

OK is this game like a single rocket/bird/person and a bunch of falling or moving asteroids/pipes/pigs?

Simon

[chaucer345]

Hi chaucer345,
I think it would be best to start here;

Code: Select all

if  intersect (the top of image pUp,Rectangle1) then

if that works for you then add the rest 1 by 1 testing each time.

So, you have 4 images colliding with 10 rectangles.
Do you need to use "top"? Wouldn't any intersect work for you? Yes, yes I know it's the top of the image because this is a vertical slider. but any intersect would do wouldn't it?

OK is this game like a single rocket/bird/person and a bunch of falling or moving asteroids/pipes/pigs?

Simon

The four images are four pictures of the player moving in an upwards, downwards, left and right direction. The rectangles I'm checking against are meerly the walls of the room that I want the player to stop at.

I think the full code for the card might be useful here:

Code: Select all

local intersectst 
local intersectsb
local intersectsl
local intersectsr

on preOpenCard
   show image pRight
   hide image pLeft
   hide image pUp
   hide image pDown
   put false into intersectst
   put false into intersectsb
   put false into intersectsl
    put false into intersectsr
end preOpenCard

on arrowKey nMessage
   if nMessage is "down" then
      checkIntersects
      if intersectsb is false then
      set the top of image pUp to the top of image pUp + 10
      set the top of image pDown to the top of image pDown + 10
      set the top of image pLeft to the top of image pLeft + 10
      set the top of image pRight to the top of image pRight + 10
      end if
      hide image pUp
      hide image pLeft
      hide image pRight
      show image pDown
   else if nMessage is "up" then
      checkIntersects
      if intersectst is false then
      set the top of image pUp to the top of image pUp -10
      set the top of image pDown to the top of image pDown -10
      set the top of image pLeft to the top of image pDown - 10
      set the top of image pRight to the top of image pRight -10
      end if
      hide image pDown
      hide image pLeft
      hide image pRight
      show image pUp
   else if nMessage is "left" then
      checkIntersects
      if intersectsl is false then
      set the left of image pUp to the left of the image pUp - 10
      set the left of image pDown to the left of the image pDown - 10
      set the left of image pLeft to the left of the image pLeft - 10
      set the left of image pRight to the left of the image pRight - 10
      end if
      hide image pUp
      hide image pDown
      hide image pRight
      show image pLeft
   else if nMessage is "right" then
      checkIntersects
      if intersectsr is false then
      set the left of image pUp to the left of image pUp + 10
      set the left of image pDown to the left of image pDown + 10
      set the left of image pLeft to the left of image pLeft + 10
      set the left of image pRight to the left of image pRight + 10
      end if
      hide image pUp
      hide image pDown
      hide image pLeft
      show image pRight
   end if
end arrowKey

command checkIntersects
   if  intersect ((the top of image pUp OR the top of image pDown OR the top of image pLeft OR the top of image pRight), (Rectangle1 OR Rectangle2 OR Rectangle3 OR Rectangle4 OR Rectangle5 OR Rectangle6 OR Rectangle7 OR Rectangle8 OR Rectangle9 OR Rectangle10)) then
      put true into intersectst
   else 
      put false into intersectst
   end if
  if  intersect ((the bottom of image pUp OR the bottom of image pDown OR the bottom of image pLeft OR the bottom of image pRight), (Rectangle1 OR Rectangle2 OR Rectangle3 OR Rectangle4 OR Rectangle5 OR Rectangle6 OR Rectangle7 OR Rectangle8 OR Rectangle9 OR Rectangle10)) then
      put true into intersectsb
   else 
      put false into intersectsb
   end if
  if  intersect ((the left of image pUp OR the left of image pDown OR the left of image pLeft OR the left of image pRight), (Rectangle1 OR Rectangle2 OR Rectangle3 OR Rectangle4 OR Rectangle5 OR Rectangle6 OR Rectangle7 OR Rectangle8 OR Rectangle9 OR Rectangle10)) then
      put true into intersectsl
   else 
      put false into intersectsl
   end if
  if  intersect ((the right of image pUp OR the right of image pDown OR the right of image pLeft OR the right of image pRight), (Rectangle1 OR Rectangle2 OR Rectangle3 OR Rectangle4 OR Rectangle5 OR Rectangle6 OR Rectangle7 OR Rectangle8 OR Rectangle9 OR Rectangle10)) then
      put true into intersectsr
   else 
      put false into intersectsr
   end if
end checkIntersects

[Simon]

I think you should group your images for the player.
Now lets just talk about a 4 walled room.

Code: Select all

if intersect(group "player", image "wall",255) then

Assuming the center of the room is transparent (alpha 0) then every time the "player" tries to move out of the box the if/then is true.

If you need help with transparencies and such just ask.

Simon

[chaucer345]

I think you should group your images for the player.
Now lets just talk about a 4 walled room.

Code: Select all

if intersect(group "player", image "wall",255) then

Assuming the center of the room is transparent (alpha 0) then every time the "player" tries to move out of the box the if/then is true.

If you need help with transparencies and such just ask.

Simon

I noticed the group objects thing, but I haven't been able to figure out how to label grouped objects. How is it done?
Also, it's kind of important for me to be able to tell if the player collided with a wall from the top, bottom left or right because I need to make sure that if they hit something from one direction they can't move further in that direction, but ensure they can still move in other directions (flypaper syndrome is a very cruel taskmaster). Do you have any advice for adapting the system to accommodate that?
Also, what's the 255 for?

[Simon]

...from one direction they can't move further in that direction

Ok, yes then you need the four images, still I think you want to group them together to keep them moving in unison. Here is a lesson on grouping;
http://lessons.runrev.com/m/4071/l/1303 ... iple-cards
They use the old Application Browser, not the Project Browser but they both work.
But is "top" still needed?

Also, what's the 255 for?

Ahhh I thought you'd ask that. From the Dictionary;

alpha value - An integer between 0 and 255 which specifies a threshold that the alpha value of each pixel must be greater than or equal to in order to be counted during calculation of the intersect.

It's the opacity/transparency of an image, are you familiar with those terms?

Simon

[chaucer345]

I am familiar, I've seen the word pixels used in similar statements to avoid blank space causing collisions.

[Simon]

Hi chaucer345,
No need to quote my entire post... really I'm still just right here.
Simply, 255 means a solid pixel, 0 is completely transparent and then there are all the ones in between.

Simon

[chaucer345]

Sorry about that! Quote Yanked.

Still, does the objects not being grouped explain the error message?

[Simon]

Still, does the objects not being grouped explain the error message?

I dunno...
Tell me what happens when you use just a single image and a single rectangle.
Then 1 image and 2 rects, then 2 images and 2 rects.
Maybe you can't use an "and" or "or" in the function. If you tell me then we'll both know.

Simon

[JackieBlue]

What about Switch Case? Any time you have a multiple (well, more than 2) cases I use a Switch Case (Select Case in other languages).

[SparkOut]

I think this is a great learning exercise, but I can't stop myself from mentioning Animation Engine and looking up constrainRectangular (and other constrain variants).
For the complex if...then I agree a switch construction would be much clearer. And agree with the advice to help resolve the boolean AND/OR cases one by one - and it helps me to put parentheses round each case to clearly see what the engine will see. Every one of those needs to resolve to a true or false state, and while constructing, splitting those parenthesised cases onto separate lines in your script editor could help.