Do loop

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New Contributor
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Accepted Solution

Do loop

Hi,

 

Can anyone help me to understand why the final output x= 5 index = 7 appear?

 

Code:


data work.loop;
x = 0;
do index = 1 to 5 by 2;
x = index;
output;
end;
output;
run;

 Output: 

Capture.PNG


Accepted Solutions
Solution
‎05-29-2018 08:22 AM
Super User
Super User
Posts: 9,599

Re: Do loop

Posted in reply to vincentgoh88

Just simply follow the logic:

	do index = 1 to 5 by 2;
x = index;
output;
end;
output;

Index starts at 1, x is set to it.  Then it is output

Then 3, x is set to it.  Then it is output

Then 5, x is set to it, then it is output. 

Then index becomes 7, which does not work in the do, so the do loop is jumped, and then next step is output, which outputs the 7 record.  X remains as 5, as the part in the do loop is not executed.

 

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Solution
‎05-29-2018 08:22 AM
Super User
Super User
Posts: 9,599

Re: Do loop

Posted in reply to vincentgoh88

Just simply follow the logic:

	do index = 1 to 5 by 2;
x = index;
output;
end;
output;

Index starts at 1, x is set to it.  Then it is output

Then 3, x is set to it.  Then it is output

Then 5, x is set to it, then it is output. 

Then index becomes 7, which does not work in the do, so the do loop is jumped, and then next step is output, which outputs the 7 record.  X remains as 5, as the part in the do loop is not executed.

 

New Contributor
Posts: 2

Re: Do loop

Thanks!
Super Contributor
Posts: 339

Re: Do loop

Posted in reply to vincentgoh88

Hi,

 

The do loop continues looping until the upper limit is exceeded, so after the loop has processed the index of 5, index is increased by 2 which becomes 7 which exceeds the upper limit of the loop and so it is not executed again; x is not reassigned again so it is left with its last value of 5.

 

Regards,

Amir.

Super User
Posts: 10,778

Re: Do loop

Posted in reply to vincentgoh88

After DO LOOP ,index will +2 by itself , therefore, the last index is 7 .

Super User
Posts: 10,249

Re: Do loop

Posted in reply to vincentgoh88

Basically all languages that I know implement iterative loops like that.

Only loops where the "index variable" is set from a list (eg see "for" in UNIX shell scripting) terminate differently.

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