Hi all

Revised the documentation

But I still haven’t found a clear answer

Essence:

There is a cycle - FOR/WHILE...

Question: up to what nesting level is the EXIT or CONTINUE valid?

Example below:

1 - - - - - - -

FOR i:=1 to 10 do

if i < 5 then

EXIT;

end_if;

END_FOR;

2- - - - - - -

FOR i:=1 to 10 do

n:=n+1;

if i < 10 then

if n > 5 then

EXIT;

end_if;

end_if;

END_FOR;

In practice, example 1 always works, example 2 does not always work.

The question is why?

I tried testing this on different PLCs.

At 1200/1500 and 300

However, example 1 always worked accurately, example 2 did not always work equally and accurately.

At the same time, there were obvious overflows in the loops, that is, according to the example 1, the value of “i” was greater than 10 and this needed to be controlled...

I wrote that what is the problem

The problem is that this doesn't always work.

Tests were carried out on different PLCs

The problem is that when the “exit” instruction is folded inside a loop, there is no 100% guarantee that it will work (Exactly when she is inside the 2nd level condition).

The question is - is this how it should be?

That is, inside the loop we should put similar instructions only at the first level of conditions???

1)

FOR #x := 1 TO #T_CC_NS DO

  IF #x <= #T_CC_NS THEN

This IF statement will be allways TRUE and not necessary. 

IF ("Shuttle".ConvShuttles[#iCCNA, #x].iNSending = #T_CC_CC_Number[#i] OR

  "Shuttle".ConvShuttles[#iCCNA, #x].iNReserved = #T_CC_CC_Number[#i]) AND

  "Shuttle".ConvShuttles[#iCCNA, #x].bWaiting THEN

  #T_CurrentShuttlePos := "Shuttle".Shuttles[#iCCNA, #x].diShuttleShiftPos + #T_StartPos;

  EXIT; (Within this condition, exit does not always occur.)

The condition is correct? How you test it? 

Hello @Unreality.

The EXIT instruction applies to the FOR loop only (within the examples). The IF statement should not effect it. The EXIT should also only effect the nearest loop.

@Michael has a good point in wanting to ask how you came by the conclusion that the EXIT instruction is not working. Part of that is also that we do not know what you were expecting and what is it actually doing.

The test code you presented has been made to run for 30s. The Scope recorded the results for the duration. The code executed as I have expected. See the attached file.

@Gustavo makes some valid arguments about your application code. It leaves me to wonder why you have put in the structure as you have done. Perhaps it is worth mention some points.

FOR #i := 1 to #nr DO

  ; // code

END_FOR;

• +1 increment is assumed when the increment is not specified
• #nr < 1 .. the FOR loop will not run
• #nr = 1 .. the FOR loop will run once
• #nr > 1 .. the FOR loop will run #nr of times

Sometimes we need some combined conditions to allow the loop to run. The alternatives to FOR is WHILE and REPEAT provide that complexity. WHILE tests the conditions before executing the code in the loop. REPEAT will execute the code inside the loop at least once.

What are your thoughts? How can the forum help?