For loop explanation

QMS_MAN · Aug 12, 2015

Hi All,

Please could somebody explain step by step the following statement.

FOR I:=1 TO 100 BY 2 DO
IF ARR = 70
THEN J:=I;
EXIT;
END_IF;
END_FOR

Kind regards..

scrambled · Aug 12, 2015

The code is traversing through the first 100 elements of array 'ARR' and saving into variable 'J' the index of the first element that has a value of 70.

QMS_MAN said:
FOR I:=1 TO 100 BY 2 DO

Not too familiar with the 'BY 2' part. My guess is that it means only look at every second element of the array. I'd consult manuals for whatever hardware or software environment you grabbed this bit of code from.

JesperMP · Aug 12, 2015

(deleted) I must have been temporarily insane.

i increments by the uneven numbers 1 - 3 - 5 - 7 etc.

TL140 · Aug 12, 2015

QMS_MAN said:
Hi All,

Please could somebody explain step by step the following statement.

FOR I:=1 TO 100 BY 2 DO
IF ARR = 70
THEN J:=I;
EXIT;
END_IF;
END_FOR

Kind regards..

FOR I: =1 is setting variable I to 1.

TO 100: this loop will run until I >= 100 and then break.

BY 2 is the incremental value. 1+2=3. 3+2=5. etc...

IF ARR = 70: This is saying that if any of the elements in the array are equal to 70 then do the following:

THEN J:= I: Set variable J equal to the element number of the the array which is equal to 70. After that, exit the for loop completely.

Ex. ARR = [144, 42, 23, 41, 34, 70, 34, 99, etc...]

(dependent on the processor, the array element will start at 0 or 1. In this example I'll say it starts at 0 since i'm more used to that.)

the loop looks at element #1. It says ARR[1] = 42. the IF statement is false so I wont do anything.

I increments by 2.

ARR[3] = 42. IF statement is false. It gets skipped.

I increments by 2.

ARR[5] = 70. That makes the IF statement true.

Now we set J = 5.

Now we exit the FOR loop because thats all the info we need due to the EXIT command.

QMS_MAN · Aug 12, 2015

Thanks to everyone for the answers, has been very use full and cleared up my confusion.

Kind Regards

For loop explanation

QMS_MAN

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scrambled

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JesperMP

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TL140

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QMS_MAN

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