How to check if the list is empty

[makset]

Hello.
I have the following problem with sas list:

%let List =;
%let N_List = %sysfunc(countw(&List));

533 %let List =;
534 %let N_List = %sysfunc(countw(&List));
ERROR: The function COUNTW referenced by the %SYSFUNC or %QSYSFUNC macro function has too few
arguments

%if &list =  %then %do;
..
%end;

ERROR: A character operand was found in the %EVAL function or %IF condition where a numeric 
       operand is required. The condition was: &list = 

How to check if the list is empty???

Thank you very much for all your help

[yabwon]

%if %superq(list) =  %then %do;
...
%end;

[PeterClemmensen]

Use a proper macro quoting function or make sure that the &list macro variable is available in the local symbol table for your macro (i.e. create it inside the macro def).

[Tom]

If you give %SYSFUNC() at least two arguments then it will not cause the COUNTW() function to issue that error.

937   %let List =;
938   %let N_List = %sysfunc(countw(&List,));
939   %put &=n_list;
N_LIST=0

But you really should be telling COUNTW() what delimiters to use.  For example a space.

%let N_List = %sysfunc(countw(&List,%str( )));

Otherwise it uses multiple characters.

the default delimiters depend on whether your computer uses ASCII or EBCDIC characters.

• If your computer uses ASCII characters, then the default delimiters are as follows:

  blank ! $ % & ( ) * + , - . / ; < ^ |

  In ASCII environments that do not contain the ^ character, the SCAN function uses the ~ character instead.
• If your computer uses EBCDIC characters, then the default delimiters are as follows:

  blank ! $ % & ( ) * + , - . / ; < ¬ | ¢

To simply test if the sting is empty I normally just test for non-zero length.

%if %length(&list) %then ...