SAS Advanced Exam

[Alass006]

Hello there,

I am reaching out for sas question and wondering if you can assist me in explaining the right anwer.

The following SAS program is submitted:

%macro mysum(n);

%if &n > 1 %then %eval(&n + %mysum(%eval(&n-1)));

%else &n;

%mend;

%put %mysum(4);

Which output is written to the log?

A. 10

B. 4+3+2+1

C. 7

D. A character operand was found in the %EVAL function or %IF condition where a numeric operand is required.

correct_answer = "A"

I would go for "C."  I have access to enterprise guide but nothing is written to the  log.

[Urban_Science · Accepted solution]

I think you are getting 7 because you are not following the recursion all the way through.  Notice that in the %if statement that %mysum is called again, except with &n -1. Think about what %mysum(3) returns.  

Also, unless you have settings to prevent %put from outputting to the log, I think the answer is getting buried in the line execution numbers.  This is what mine looks like after being ran:

1 %_eg_hidenotesandsource;
5 %_eg_hidenotesandsource;
31
32 %macro mysum(n);
33
34 %if &n > 1 %then %eval(&n + %mysum(%eval(&n-1)));
35
36 %else &n;
37
38 %mend;
39
40 %put %mysum(4);
10
41
42 %_eg_hidenotesandsource;
57
58
59 %_eg_hidenotesandsource;

Notice that 10 is in there right between line 40 and 41.

Something that I do when I am debugging my macros is to add log notes when the macro is called.  For example: 

%macro mysum(n);

%put mysum called: n=&n;

%if &n > 1 %then %eval(&n + %mysum(%eval(&n-1)));

%else &n;

%mend;

%put %mysum(4);

you can then see it being called 4 total times in the log: 

42 %put %mysum(4);
mysum called: n=4
mysum called: n=3
mysum called: n=2
mysum called: n=1
10

43

[Alass006]

Thank you much !

[ballardw]

I don't use EG but you might try changing the final %put to this:

%put NOTE: Final value of mysum macro is: %mysum(4);

so the result stands out more. If the log uses different appearance for NOTE: WARNING: and ERROR: entries it is likely the result will have those appearance options.

[raawan]

WHEN IS IT GOOD TO COMBINE MULTIPLE SAS DATASETS BY MATCHING KEY VALUES??

WITH INDEXES ON KEY VALUES OR WITHOUT INDEXES ON KEY VALUES