Please explain me step by step

[soujik]

%macro dt_date(date=,interval=,format=,offset=-1,alignment=B,quote=Y)/minoperator;
%put Start macro dt_date(date=&date,interval=&interval,format=&format,offset=&offset,alignment=&alignment,quote=&quote);

%local interval_temp;

%local d fmt rc dsid;

%if %superq(date)=%str() %then %let date=&dt_sas;

%let interval=%upcase(&interval);

%let quote=%upcase(&quote);

%let alignment=%upcase(&alignment);

%if &format ne %str() %then
%do;

%let fmt=%upcase(%sysfunc(compress(&format,%str(.),d)));

%let dsid=%sysfunc(open(sashelp.vformat(where=(fmtname="&fmt"))));

%let rc=%sysfunc(fetch(&dsid));

%let dsid=%sysfunc(close(&dsid));

%if &rc=-1 %then
%do;

%let errormsg1=&format is not a valid format.;

%let jumptoexit=1;

%let d=;

%goto EXIT;

%end;

%end;
%else
%do;

%let format=best.;

%let quote=N;

%end;

%let interval_temp=%scan(&interval,1,%str(.));

%let pos=%sysfunc(anydigit(&interval_temp));

%if &pos %then %let interval_temp=%substr(&interval_temp,1,%eval(&pos-1));

%if %eval(&interval_temp in YEAR QTR MONTH WEEK DAY YEARLY QUARTERLY MONTHLY WEEKLY DAILY)=0 %then
%do;

%let errormsg1=&interval is not a valid date interval.;

%let jumptoexit=1;

%let d=;

%goto EXIT;

%end;

%if %sysfunc(inputn(&offset, best.))=%str() %then
%do;

%let errormsg1=&offset is not a valid offset.;

%let jumptoexit=1;

%let d=;

%goto EXIT;

%end;

%if &quote ne Y and &quote ne N %then
%do;

%let errormsg1=&quote is not a valid Quote value. Must be Y or N.;

%let jumptoexit=1;

%let d=;

%goto EXIT;

%end;

%if &alignment ne B and &alignment ne E and &alignment ne M and &alignment ne S %then
%do;

%let errormsg1=&alignment is not a valid alignment value. Must be B, E, M, S.;

%let jumptoexit=1;

%let d=;

%goto EXIT;

%end;

%let date=%sysfunc(intnx(&interval,&date,&offset,&alignment));

%let d=%sysfunc(putn(&date,&format));

%if %superq(d)=%str() %then
%do;

%let errormsg1=&format is not a valid format.;

%let jumptoexit=1;

%let d=;

%goto EXIT;

%end;

%if &quote=Y %then %let d=%unquote(%str(%')&d%str(%'));

%EXIT:

%unquote(&d)

%put End macro dt_date - Date Value returned is %unquote(&d);
%mend dt_date;

[Patrick]

This code demonstrates why developers should spend the time to add inline comments with explanations. 

I believe a "explain everything" is likely a too big ask for this forum. 

I just tried and asked ChatGPT to explain the code. The answer wasn't too bad. I suggest you try this first and then come back here with some targeted detail questions should there still be a need. ....and of course if there are just some macro functions you don't understand first consult the SAS docu.

[SASKiwi]

Adding to @Patrick 's comment about lack of comments, there is a complete lack of proper code layout to make it at least readable. That includes having blank lines between sections and indenting %DO blocks.

[WarrenKuhfeld]

Adding to the other comments. Don't use the macro language when you can use ordinary SAS code. I wrote some multi-thousand line macros in my day. Of course they had macro code. That said, when ever possible, I used DATA _NULL_ DATA step code to process parameters and strings. It makes your life much easier.

[Tom]

It is an over complicated way to call the INTNX() function.

%sysfunc(intnx(&interval,&date,&offset,&alignment),&format)

If you are interested here is a partial list of the logic/coding mistakes:

Spoiler

Adds the / MINOPERATOR option to the %MACRO statement and then does not use IN as an operator (even in places where it would make sense in this program).

Use of "magic" macro variables.  Referencing a macro variable in the middle of the macro that not an input and has no comment or other code explaining where its value should come from.

%if %superq(date)=%str() %then %let date=&dt_sas;

Assumes that just removing the period from a format specification will result in the bare format name.

  %let fmt=%upcase(%sysfunc(compress(&format,%str(.),d)));

Using BEST as the name of an INFORMAT 

%if %sysfunc(inputn(&offset, best.))=%str() %then %do;

Assuming that PUTN() will return an empty string when the value is missing instead of the normal single period.

%let d=%sysfunc(putn(&date,&format));
%if %superq(d)=%str() %then %do;

Unquoting a value that was never quoted.

%unquote(&d)

And for something that is going to a lot (too much really) trouble to validate its input it will stop the macro when the first invalid input is detected.  So if a user has made mistakes on multiple inputs they will have to make many calls to discover all of the parameter errors they have made.

[Tom]

Note it does not handle this format:

461  %put %dt_date(date='01JAN2023'd,interval=month,format=e8601da.,offset=-1,alignment=B,quote=Y);
Start macro dt_date(date='01JAN2023'd,interval=month,format=e8601da.,offset=-1,alignment=B,quote=Y)
End macro dt_date - Date Value returned is

462  %put %sysfunc(intnx(month,'01JAN2023'd,-1,b),e8601da.);
2022-12-01

[s_lassen]

I think I found out why - another error in the macro:

%let fmt=%upcase(%sysfunc(compress(&format,%str(.),d)));

This removes all digits from the format name, including the "8601" in "E8601DA.", so the format name becomes "EDA". The code does not flag this error though, as the  code

%let errormsg1=&format is not a valid format.;

does not  write the error message anywhere (and the variable is %LOCAL, unless it has been defined outside the macro).

For those who want to see what the macro does, here is a version in readable format:

%macro dt_date(date=,interval=,format=,offset=-1,alignment=B,quote=Y)/minoperator;
  %put Start macro dt_date(date=&date,interval=&interval,format=&format,offset=&offset,alignment=&alignment,quote=&quote);
  %local interval_temp;
  %local d fmt rc dsid;

  %if %superq(date)=%str() %then %let date=&dt_sas;
  
  %let interval=%upcase(&interval);
  %let quote=%upcase(&quote);
  %let alignment=%upcase(&alignment);
  
  %if &format ne %str() %then %do;
    %let fmt=%upcase(%sysfunc(compress(&format,%str(.),d)));
    %let dsid=%sysfunc(open(sashelp.vformat(where=(fmtname="&fmt"))));
    %let rc=%sysfunc(fetch(&dsid));
    %let dsid=%sysfunc(close(&dsid));
    %if &rc=-1 %then %do;
      %let errormsg1=&format is not a valid format.;
      %let jumptoexit=1;
      %let d=;
      %goto EXIT;
      %end;
    %end;
  %else %do;
    %let format=best.;
    %let quote=N;
    %end;

  %let interval_temp=%scan(&interval,1,%str(.));
  %let pos=%sysfunc(anydigit(&interval_temp));
  %if &pos %then %let interval_temp=%substr(&interval_temp,1,%eval(&pos-1));
  
  %if %eval(&interval_temp in YEAR QTR MONTH WEEK DAY YEARLY QUARTERLY MONTHLY WEEKLY DAILY)=0 %then %do;
    %let errormsg1=&interval is not a valid date interval.;
    %let jumptoexit=1;
    %let d=;
    %goto EXIT;
    %end;

  %if %sysfunc(inputn(&offset, best.))=%str() %then %do;
    %let errormsg1=&offset is not a valid offset.;
    %let jumptoexit=1;
    %let d=;
    %goto EXIT;
    %end;

  %if &quote ne Y and &quote ne N %then %do;
    %let errormsg1=&quote is not a valid Quote value. Must be Y or N.;
    %let jumptoexit=1;
    %let d=;
    %goto EXIT;
    %end;

  %if &alignment ne B and &alignment ne E and &alignment ne M and &alignment ne S %then %do;
    %let errormsg1=&alignment is not a valid alignment value. Must be B, E, M, S.;
    %let jumptoexit=1;
    %let d=;
    %goto EXIT;
    %end;

  %let date=%sysfunc(intnx(&interval,&date,&offset,&alignment));
  %let d=%sysfunc(putn(&date,&format));
  %if %superq(d)=%str() %then %do;
    %let errormsg1=&format is not a valid format.;
    %let jumptoexit=1;
    %let d=;
    %goto EXIT;
    %end;


  %if &quote=Y %then %let d=%unquote(%str(%')&d%str(%'));

  %EXIT:
%unquote(&d)

%put End macro dt_date - Date Value returned is %unquote(&d);
%mend dt_date;