Re: problem with shoot procedure

[Timothy Klein <kleinvox@xxxxxxx>]

On 31 Jan 2008, at 9:49 AM, zehava wizman wrote:

> hello forum!
> I send this problem to LOGO FORUM , some of the friends told me
> that the forum can't read attaced file, so maybe,I could get help
> from you ( as I got  good solution some monthes before).
> I use MW Pro  ver 1.1
> I have 2 problem:
> 1. When I used the key (space) whenever I want to shoot, Its working
> well till its stopped and an error message "I can't start new  
process" ,
> when I used a button (only for shoot) Its working well,WHY?
> 2. Shoot proc checks whether one turtle touches other, then the
> turtle has to be hidden, there is within the if condition an  
instruction
> naming the turtle to be hidden, and it doesn't do it. WHY?
> thanks,  Zehava



----------
Problem 1.

The MicroWorlds 'when' command launches and independent, parallel  
process. That means that the 'when' keeps doing its thing in the  
background, forever, unless you specifically use a 'cancel' command  
to stop it.
The "I can't start a new process" error is probably due to that. You  
see, you launch *brand new* 'when' process, (five of them) every time  
you shoot. And you're not telling them all to go away. So eventually  
MicroWorlds reaches its built-in limit for the number of processes it  
can handle (this is my guess, at least -- I never got the error. But  
I use EX on a fairly modern Mac, and you are using Pro: the number of  
process allowed could be very different for each of us, especially if  
you computer is older).
How to make this go away? Use the 'cancel' command. I simply changed  
your 'shoot' procedure to include this at the beginning:
  cancel [ touching? "bullet "t1 ]
  cancel [ touching? "bullet "t2 ]
  cancel [ touching? "bullet "t3 ]
  cancel [ touching? "bullet "t4 ]
  cancel [ touching? "bullet "t5 ]

This gets rid of any useless 'when' commands from the last bullet  
shot -- we don't need them anymore, as that bullet no longer exists.  
And we're going to make brand new 'when' commands for the next shot.
You can see this happening live in your 'Processes' tab: there will  
be many 'when [ touching ...]' instructions, and they keep on  
multiplying.
----------
Problem 2.

This one took me the longest, but it was actually quite simple! Your  
turtles are not hiding because you unhide them! In the 'shoot'  
procedure, you do hide the plane if it gets shot (with 'ht'). The  
trouble is in your 'fly' procedure: it repeats 'forever', and one of  
the instructions there, sent to every plane, is 'st'. So right after  
you hide a plane that gets shot, you bring it back to life! Oops. :-)
I fixed this by giving each plane a 'clickon' instruction that was  
identical to your instructions inside the 'forever' inside 'fly'  
*except* I took out the 'st' command. Then, in 'fly' I just asked  
each plane to 'clickon'. And then in 'shoot', if a plane gets hit, I  
asked it to hide itself with 'ht', and then 'clickoff.' Now, the  
plane is not being asked to repeatedly show itself with 'st' inside  
the 'forever' loop of fly:
to fly
  ask [plane1 plane2  plane3  plane4  plane5]
    [ clickon ]
end

; clickon instruction for each plane
to plane_path
  seth 270
  fd 10
  wait 1
  setsh 16
  setsize 10
end

Showing the planes is an *initialization* action, not something we  
want to do repeatedly as they fly. This is a common programming error  
to make.
So, to make sure every plane comes back to life at the beginning of a  
new game, in the 'start' procedure I asked each plane to show itself  
with 'st', in case they were hidden last time because they were shot:
to start
  forever [keys]
  ask [ plane1 plane2 plane3 plane4 plane5 ]
    [ st ]
  fly
  setpoints 0
  bullet,
    ht
end

One last tip: in you 'shoot' procedure, you blow up each plane in an  
identical way, and repeat that code 5 times. Any time you see  
something like this, it's a good place to write a procedure:
  when [touching? "bullet "plane1]
  [
    bullet,
      clickoff
      ht
    plane1,
      blowup
  ]

etc... and then:

; a plane got shot
to blowup
  setsize 50
  setsh 19
  wait 2
  ht
  setpoints points + 1
  clickoff
end

I did my work in EX, as I said above, and you are using Pro, so I  
can't give you the modified project. But I'll attach a text file with  
the code -- it's heavily modified, but it is mostly cosmetic. I  
changed the formatting so that I could understand your code better.  
And I moved code out of the turtle's 'instruction' and into the  
procedures tab, as 'bullet_path' for the bullet, and 'plane_path' for  
the planes. I then changed those turtles' instructions to those  
procedures. I also added a 'blowup' procedure to eliminate the  
repeated code for blowing up planes. And I gave the planes better  
names. And added some comments and indents.
Try and make sure you understand the changes, though -- don't just  
copy the code into your project. MicroWorlds works best if *you*  
figure it out. See if you can fix your code from this email *before*  
looking at my code, preferably without just copying and pasting.  
Also, the attached text file with MicroWorlds Logo code has Windows/ 
DOS line endings. Send me an email if you need Mac/Unix line endings.
I hope this helps.

Sincerely,

Timothy Klein
--
Teacher, OpenWorld Learning
tklein@xxxxxxxxxxxxxxxxxxxxx