• Introduced in SAS 9.4M3
• Lua is a lightweight scripting language designed primarily for embedded use in applications. Written in C.
• Comparing to alternatives (like PROC GROOVY) has much less overhead and is easier to use.

ERROR: SUBMIT block:2: attempt to call a table value
stack traceback:
    SUBMIT block:2: in function 'iterate'
    SUBMIT block:9: in function 'times'
    SUBMIT block:13: in main chunk
ERROR: There was an error submitting the provided code
NOTE: The SAS System stopped processing this step because of errors.

ERROR: An unexpected semicolon occurred in the %DO statement. A dummy macro will be compiled.

Intro

• Visual performance overview using Enterprise Session Monitor (ESM) for SAS — software by Boemska
• Performance monitoring can be also obtained in SAS with Application Response Measurement (ARM)

For loop (n=1e7)

%do i = 1 %to &n;
  %put &i;
%end;

for i = 1, n do
  print(i)
end

For loop – overview

For loop – Lua

For loop – SAS Macro

Utility files in WORK

$ ls -al
-rw-r--r-- 1 sasdemo 88039424 Oct 20 19:57 #tf0024.sas7butl
drwx------ 2 sasdemo     1024 Oct 20 19:57 .
drwx------ 3 sasdemo       96 Oct 20 19:56 ..
-rw-r--r-- 1 sasdemo    12288 Oct 20 19:57 sasmac1.sas7bcat

Iterating over a list (n=1e5)

%let list=George Paul Ringo John Foo Bar Baz Macro Polo;

%do i = 1 %to
  %sysfunc(countw(&list));

  %let item=%scan(&list, &i);
  %put &item;
%end;

list = {"George", "Paul", "Ringo", "John", "Foo", "Bar", "Baz", "Macro", "Polo"}

for _, i in ipairs(list) do
  print(i)
end

Iterating over a list

Iterating over a list – Lua

Iterating over a list – SAS Macro

Reading a dataset (1900000 observations, 73mb, 5 variables)

data class(drop=i);
  set sashelp.class;
  do i = 1 to 100000;
    output;
  end;
  drop i;
run;

Reading a dataset – SAS Macro code

%let dsid = %sysfunc(open(&indat));
%syscall set(dsid);
%let nobs = %sysfunc(attrn(&dsid, nlobs));
%do i=1 %to &nobs;
  %let rc = %sysfunc(fetchobs(&dsid, &i));
%end;
%let rc = %sysfunc(close(&dsid));

Reading a dataset – Lua code

dsid = sas.open('class')
while sas.next(dsid) do
  name = sas.get_value(dsid, 'name')
  sex = sas.get_value(dsid, 'sex')
  age = sas.get_value(dsid, 'age')
  height = sas.get_value(dsid, 'height')
  weight = sas.get_value(dsid, 'weight')
end
sas.close(dsid)

Reading a dataset – overview

Transpilers

• PROC DSTODS2 in SAS
• DATA Step is a SAS to C transpiler
• Typescript to Javascript
• C++ was a transpiler to C at the early development

SAS Macro to Lua tranpiler

/* mf_existds.sas */
/* @number */

%macro mf_existds(libds);
  %if %sysfunc(exist(&libds))      ne 1 &
      %sysfunc(exist(&libds,VIEW)) ne 1 %then 0;

  %else 1;
%mend;

%put {%mf_existds(sashelp.class)};

Lua equivalent

-- mf_existds.lua

function mf_existds(libds)
  if sas.exist(libds) ~= 1 and 
     sas.exist(libds, 'VIEW') ~= 1 then

    return 0
  else
    return 1
  end
end

print('{'..mf_existds('sashelp.class')..'}')

ANTLR

Demo

Tree traversal

Sasensei quizz (Lua, SAS Macro, regex questions)

https://sasensei.com/test/131