QUITTING from 2 NESTED REPEAT loops, when the inside loop quits?

DavidM

Hi,

I have two nested repeat loops

REPEAT X From 1 To 10

  REPEAT Y From 1 To 10

    IF CheckSomething := TRUE

        DoSomething(X,Y)
        QUIT ' Quit from Y loop

If the DoSomething line of code executes I want to QUIT from both loops, So Far I can only QUIT from the Inside (Y loop).

The X or Y values can be any value when the loops need to quit, so I can't monitor these two variables to quit the Outside loop,
So I could only use ANOTHER Local variable ( boolean) that will be set when the dosomething statement is executed.

Like this..

StopOutsideLoop := FALSE

REPEAT X From 1 To 10

  REPEAT Y From 1 To 16

    IF CheckSomething := TRUE

        DoSomething(X,Y)
        StopOutsideLoop == True
        QUIT ' Quit from Y loop

  IF StopOutsideLoop
     QUIT ' Quit the outside loop

Any Ideas if this is possible without another variable?



Thanks
Dave M

Paul G

Could you not use 1 loop variable and then modulus and remainder ? Something like this:

REPEAT x from 0 to 159

  IF CheckSomething := TRUE

    DoSomething(x/16 +1, x//16+1)
    QUIT

Post Edited (Paul G) : 8/4/2010 8:29:16 AM GMT

kuroneko

If it's more about readability then you could try something like this if division and remainder calculations are too expensive (incomplete):

repeat
  repeat
    active := fn(x, y)
  while --y and active
while --x and active

Also, your

IF CheckSomething := TRUE

should probably read

IF CheckSomething == TRUE

or simply

IF CheckSomething

The way it's now it will always evaluate to TRUE.

Post Edited (kuroneko) : 8/4/2010 8:32:29 AM GMT

DavidM

Hi kuroneko, & paul G

Interesting suggestions!

sorry that was a typo, should have been as you said "IF CheckSomething == TRUE"

Thanks for the suggestions,

READABILITY is important, I have enough ( hard to read Code as it is) , I like to keep the decision logic easy to read where possible.

Thanks

Dave M

Baggers

Quick easy hack is to put it in it's own PUB that way, when you want to exit the routine, you just return [noparse]:D[/noparse]

PUB quittableroutine
  repeat y from 0 to 99
    repeat x from 0 to 99
      dosomething
      if quitting==1
        return

Hope this helps [noparse]:D[/noparse]

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DavidM

Hi Baggers


That's it!!!

I do have this as its own METHOD so that idea of yours should work!


Thanks

Dave M

virtuPIC

Uh! Ever heard about structured programming? I know, there is no such thing in assembler. But in high level languages it basically means that control flow is not arbitrarily messed up but you only have reasonable constructs that guarantee only to leave one loop level at a time.

However, even in this case there is a dirty solution. Simply change the index variable of the outer loop to trick the loop condition:

REPEAT X From 1 To 10 'Value might also be changed inside loop

  REPEAT Y From 1 To 10

    IF CheckSomething := TRUE

        DoSomething(X,Y)
        x := 10
        QUIT ' Quit from Y loop

Not really nice since one might expect a repeat-variable only to be changed by loop control. Yes, you should really put a comment at the loop header!

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kuroneko

Baggers said...
Quick easy hack is to put it in it's own PUB that way, when you want to exit the routine, you just return [noparse]:D[/noparse]

I was just going to suggest a flavour of abort but a return seems less evil [noparse]:)[/noparse]

DavidM

Hi VirtualPic,

Your suggestion to MODIFY X , is what I wirst did to solve the problem , before posting my question here,
Variable X & Y are passed onto another method, I need to trap the Value of X & Y WHEN the Condition is met, So changing X to 10, stuffs things UP. ( i did this earlier today!)

Ideally SPIN needs to be able to NEST/INDENT QUIT Commands, i.e 2 x QUIT commands would QUIT 2 REPEAT Loops, Similar to the use of the END statement in other languages.

But we don't have that, so

A Simple extra Local variable works well, and most import it is easy to read and understand a year later if I have to visit my code again.

I have bucket loads DECISION LOGIC in my current application, SPIN is so far doing a good job of it.

One thing I have learned is to MAKE AS MANY METHODS as you need, ( even if only used once ) to keep the DECISION LOGIC much easier to read, remember all that branching can spread out over more than one screen , so its best to only have the Decision logic and then use SINGLE LINE CALLS to the TASK's ( i.e Methods )

regards

Dave M

PS I am not really familiar with the term STRUCTURED PROGRAMMING , But I am familiar with OOP, I gather that is similar. I have been doing a lot of work in REALBASIC, its an excellent language, a lot of what I have learned their I have tried to apply to SPIN.


PSS , Sometimes you just have to get code WORKING FIRST ( proof of concept) , and then RE-STRUCTURE/ optimise LATER ( I do this in stages )

virtuPIC

Well, what about making it a single loop like this:

StopOutsideLoop := FALSE

REPEAT XY FROM 1 TO 160
  IF Y > 16
    x += 1
    y := 1
  IF CheckSomething := TRUE
    DoSomething(X,Y)
    QUIT
    x := y += 1

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