Assignment Efficiency - Repetitive Assignment vs IF statement

2025-03-08T14:07:57.963000Z

Thanks for your responses. I like to write the leanest possible code that I can because it makes it much easier to read/maintain/debug.

OR_ELSE is what I was looking for. I wasn't sure if CodeSys short-circuited evaluation and I didn't realize this operator existed. Thanks!

Assignment Efficiency - Repetitive Assignment vs IF statement

2025-03-08T07:57:19.316000Z

You can consider using OR_ELSE:
Coils[0] := Coils[0] OR_ELSE (Buttons[0] AND Sensors[0] > 6);

https://content.helpme-codesys.com/en/CODESYS%20Development%20System/_cds_operator_or_else.html

IF Coils[0] is TRUE, then the rest is not relevant anymore and doesn't have to be evaluated anymore.

PS, there is also an AND_THEN
https://content.helpme-codesys.com/en/CODESYS%20Development%20System/_cds_operator_and_then.html

Assignment Efficiency - Repetitive Assignment vs IF statement

2025-03-07T06:57:50.773000Z

Its important that you know the difference between the two.

Example 1:

Coils[0] := Coils[0] OR (Buttons[0] AND Sensors[0] > 6);

In this case the statements will be evaluated every scan and result in either true or false for Coils[0].

Example 2:

IF NOT Coils[0] AND Buttons[0] AND (Sensors[0] > 6) THEN
    Coils[0] := TRUE;
END_IF

In this example Coils[0] will latch the result in a true evaluation, if you want it to behave the same way as example 1 then you need to do it like example 3 below:

IF NOT Coils[0] AND Buttons[0] AND (Sensors[0] > 6) THEN
    Coils[0] := TRUE;
ELSE
    Coils[0] := FALSE;
END_IF

However back to the real question. There is no problem using either example 1 or example 3, if im not requiring a latch i usually go with example 1 as it is more compact.

Assignment Efficiency - Repetitive Assignment vs IF statement

2025-03-07T01:55:50.554000Z

Hello

Can anyone see any problems with constant assignment as in the following statement:

Coils[0] := Coils[0] OR (Buttons[0] AND Sensors[0] > 6);

Rather than using the more verbose and vertically-larger:

IF NOT Coils[0] AND Buttons[0] AND (Sensors[0] > 6) THEN
    Coils[0] := TRUE;
END_IF

Also, is the test expression short-circuited in the latter case? In other words, will the runtime move on after it sees Coils[0] = FALSE AND?

Thanks

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Assignment Efficiency - Repetitive Assignment vs IF statement