You can use the LINK keyword, but that just keeps the PC register in a stack to return to where you were a subroutine was called, it doesn’t recreate the data vector. Because of this, all variables in a SAS Data Step behave as global within the data step block.

You could use a _TEMPORARY_ array as a stack, but its size has to be hard-coded to a predetermined depth.

SAS 9 has a rarely used Hash object, which can be used within a Data Step. It grows as needed, so it can be used to function as a functionally infinite length array, and further abused to function as a stack within a Data Step. The following code demonstrates this:

data _null_;
  declare hash stack();
  length stackvar $100;
  length stackdepth 8.;
  stackdepth=0;
  rc=stack.defineKey('stackdepth');
  rc=stack.defineData('stackvar');
  rc=stack.defineDone();

  stackvar='a';
  stackdepth+1;
  rc=stack.add();
  put 'push' stackdepth= stackvar=; 

  stackvar='b';
  stackdepth+1;
  rc=stack.add();
  put 'push' stackdepth= stackvar=; 

  stackvar='c';
  stackdepth+1;
  rc=stack.add();
  put 'push' stackdepth= stackvar=; 

  rc=stack.find();
  rc=stack.remove();
  put 'pop' stackdepth= stackvar=;
  stackdepth+-1;

  rc=stack.find();
  rc=stack.remove();
  put 'pop' stackdepth= stackvar=;
  stackdepth+-1;

  rc=stack.find();
  rc=stack.remove();
  put 'pop' stackdepth= stackvar=;
  stackdepth+-1;

  stackvar='x';
  stackdepth+1;
  rc=stack.add();
  put 'push' stackdepth= stackvar=; 

  stackvar='y';
  stackdepth+1;
  rc=stack.add();
  put 'push' stackdepth= stackvar=; 

  stackvar='z';
  stackdepth+1;
  rc=stack.add();
  put 'push' stackdepth= stackvar=; 

  rc=stack.find();
  rc=stack.remove();
  put 'pop' stackdepth= stackvar=;
  stackdepth+-1;

  rc=stack.find();
  rc=stack.remove();
  put 'pop' stackdepth= stackvar=;
  stackdepth+-1;

  rc=stack.find();
  rc=stack.remove();
  put 'pop' stackdepth= stackvar=;
  stackdepth+-1;
run;

It outputs this:

pushstackdepth=1 stackvar=a
pushstackdepth=2 stackvar=b
pushstackdepth=3 stackvar=c
popstackdepth=3 stackvar=c
popstackdepth=2 stackvar=b
popstackdepth=1 stackvar=a
pushstackdepth=1 stackvar=x
pushstackdepth=2 stackvar=y
pushstackdepth=3 stackvar=z
popstackdepth=3 stackvar=z
popstackdepth=2 stackvar=y
popstackdepth=1 stackvar=x

By doing this, you can traverse a tree in metadata.

• n – index for the nth association
• u – uri to object
• a – association

data;
  ...
  do n=1 by 1 while(n<r or r<=0);
    r=metadata_getnasl(u,n,a);
    put a;
  end;
  ...
run;

UPDATE: The metadata_getnass function has been renamed to metadata_getnasn

start <TO stop> <BY increment> <WHILE(expression) | UNTIL(expression)>

http://support.sas.com/documentation/cdl/en/lrdict/62618/HTML/default/a000201276.htm

So in another language, what might be

for(int i=0;i < max;i++) {

In SAS, you can leave out the “by 1″, since it’s the default increment. So this would be

do i=0 to max;

What’s fun is in SAS you can combine a Repeat-Until/Do-While loop with a for loop. This might be useful if for some reason you don’t set the var “max” until you’ve iterated through the loop once, such as in this case, where “metadata_getnobj” returns a negative on fail, but otherwise returns the number of objects that match the query.

do i=1 by 1 until (i >= objs);
  rc=metadata_getnobj("omsobj:SASLibrary?@Libref='MYLIBREF'",i,uri);
  if rc>=0 then objs=rc;
 
  rc=metadata_getnasn(uri,"LibraryConnection",1,uri);
  if rc>=0 then leave;
end;

This code loops through all the libraries in the metadata with libref=’MYLIBREF’, and exits with a URI for the first one it sees with at least one LibraryConnection association. This is useful when you have a remote library pointing to a local library and they both have the same name and you want a URI to the remote one.

Another cool thing with FOR loops in SAS is iteration through lists. In Java, say you have a block like this:

for(String x : new String[] { "a","b","c" }) {
  System.out.println("x="+x);
}

In SAS, this is simply

do x="a","b","c";
  put x=;
end;