Loop

[uri1616]

Hi,

The following code is doing exactly what I wanted it to do -

loop.
       
        loop.
        do if (begin = 999).
        compute turns = cnt_turns.
        compute #turns = turns.
        else if (begin NE 999).
        compute turns = #turns.
        compute #i = begin.
        end if.
        end case.
        end loop if #i=1.
       
end loop if (tape_num = $sysmis).
exe.

BUT gives this error message:

>Warning # 534
>Execution of a loop was terminated after MXLOOPS trips.  The value of
>MXLOOPS can be displayed with the SHOW command and changed with the SET
>command.

>Command line: 157  Current case: 508  Current splitfile group: 1

WHY IS THAT?

TAHNKS,
Uri

[David Marso]

That code may "doing exactly what I wanted it to do".
Probably much more efficient ways to do "it".
If only we knew what "it" was that "you wanted to do?"
--------
From the FM:

"Reference > Command Syntax Reference > SET
MXLOOPS Subcommand (SET command)

MXLOOPS specifies the maximum number of times that a loop that is defined by the LOOP-END LOOP structure is executed for a single case or input record. The default is 40.

    MXLOOPS prevents infinite loops, which may occur if no cutoff is specified for the loop structure (see LOOP-END LOOP).
    MXLOOPS will limit the number of loops for any loop structure that doesn't have an indexing clause, including loops with conditional IF clauses. If a loop has an indexing clause (e.g., LOOP #i=1 to 1000), the indexing clause overrides the MXLOOPS setting.
    When a loop is terminated, control passes to the command immediately following the END LOOP command, even if the END LOOP condition is not yet met."

uri1616 wrote

Hi,

The following code is doing exactly what I wanted it to do -

loop.
       
        loop.
        do if (begin = 999).
        compute turns = cnt_turns.
        compute #turns = turns.
        else if (begin NE 999).
        compute turns = #turns.
        compute #i = begin.
        end if.
        end case.
        end loop if #i=1.
       
end loop if (tape_num = $sysmis).
exe.

BUT gives this error message:

>Warning # 534
>Execution of a loop was terminated after MXLOOPS trips.  The value of
>MXLOOPS can be displayed with the SHOW command and changed with the SET
>command.

>Command line: 157  Current case: 508  Current splitfile group: 1

WHY IS THAT?

TAHNKS,
Uri

[Richard Ristow]

At 09:00 AM 12/29/2014, David Marso wrote, quoted uri1616, who had written,

>The following code [somewhat reformatted] is doing exactly what I
>wanted it to do, BUT gives this error message:
>>Warning # 534
>>Execution of a loop was terminated after MXLOOPS trips.
>
>loop.
>    loop.
>       do if (begin = 999).
>          compute turns = cnt_turns.
>          compute #turns = turns.
>       else if (begin NE 999).
>          compute turns = #turns.
>          compute #i = begin.
>       end if.
>       end case.
>    end loop if #i=1.
>end loop if (tape_num = $sysmis).

Like David, I've no idea what you're trying to do, because you've
left out crucial information. However, you have two loops, and at
least part of your problem is the closing statement of the outer one:

end loop if (tape_num = $sysmis).

That 'if' condition can *NEVER* be satisfied. Nothing can be "equal
to" $sysmis, because $sysmis isn't a value, in SPSS's sense; a test
of anything being "equal to" $sysmis returns 'missing'. So your outer
loop ran for MXLOOPS passes, and then gave you the warning that you saw.

The correct version of that statement is

end loop if (SYSMIS(tape_num)).

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[Richard Ristow]

At 09:00 AM 12/29/2014, David Marso wrote, quoted uri1616, who had written,

>The following code [somewhat reformatted, below] is doing exactly
>what I wanted it to do

I'm glad you're getting what you want; but the logic looks a little
strange, even correcting the syntax error I previously noted.

.  The (corrected) exit condition for the outer loop is

>end loop if (tape_num = $sysmis)  /* Corrected */.

The value of "tape_num" doesn't seem to be modified in your code; so,
even corrected, your outer loop will pass exactly once, or MXLOOPS
times, depending on whether "tape_num" is system-missing or not.

.  The exit condition for the inner loop is

>    end loop if #i=1.

It appears that this condition is satisfied if and only if the value
of "begin" is 1 at entry to this code block. So, the inner loop,
also, should be passed either once or MXLOOPS times.

>loop.
>    loop.
>       do if (begin = 999).
>          compute turns = cnt_turns.
>          compute #turns = turns.
>       else if (begin NE 999).
>          compute turns = #turns.
>          compute #i = begin.
>       end if.
>       end case.
>    end loop if #i=1.
>end loop if (SYSMIS(tape_num))  /* Corrected */.

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[Art Kendall]

Please explain in more detail what you are trying to do.

As Rich pointed out you tested whether something was equal to sysmis.

It is better practice in the long run to reserve SYSMIS for its purpose -- to indicate when the computer is not able to follow your instructions.

Any occurrence of sysmis should be a flag that you need to redraft your syntax.  User-missing values indicate that you know why the value is missing.

Are you trying to see if a variable has not been initialized, a better way is to explicitly initialize it before the section where it will be used.  Initialize it with a user-missing value.