From cfe90a8d0d5031921450302fcde2120527fa3952 Mon Sep 17 00:00:00 2001
From: trmoody <trevor@dacite.co.uk>
Date: Fri, 4 Mar 2022 00:38:07 +0000
Subject: [PATCH] chore: update to mf_getuniquelibref.sas

---
 base/mf_getuniquelibref.sas | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/base/mf_getuniquelibref.sas b/base/mf_getuniquelibref.sas
index 8fe1ef9..2fc2d78 100644
--- a/base/mf_getuniquelibref.sas
+++ b/base/mf_getuniquelibref.sas
@@ -14,27 +14,36 @@
 
 > mclib3
 
-  @param prefix= first part of libref.  Remember that librefs can only be 8 characters,
-    so a 7 letter prefix would mean that maxtries should be 10.
-  @param maxtries= the last part of the libref.  Provide an integer value.
+  A blank value is returned if no usable libname is determined.
+
+  @param prefix= first part of the returned libref. As librefs can be as long as
+    8 characters, a maximum length of 7 characters is premitted for this prefix.
+  @param maxtries= Deprecated parameter. Remains here to ensure a non-breaking
+    change.
 
   @version 9.2
   @author Allan Bowe
 **/
 
-
 %macro mf_getuniquelibref(prefix=mclib,maxtries=1000);
-  %local x libref;
-  %let x=0;
-  %do x=0 %to &maxtries;
-  %if %sysfunc(libref(&prefix&x)) ne 0 %then %do;
-    %let libref=&prefix&x;
-    %let rc=%sysfunc(libname(&libref,%sysfunc(pathname(work))));
-    %if &rc %then %put %sysfunc(sysmsg());
-    &prefix&x
-    %*put &sysmacroname: Libref &libref assigned as WORK and returned;
+  %local x;
+
+  %if ( %length(&prefix) gt 7 ) %then %do;
+    %put NOTE: The prefix parameter cannot exceed 7 characters.;
     %return;
   %end;
+
+  /* Set maxtries equal to '10 to the power of [unused characters] - 1' */
+  %let maxtries=%eval(10**(8-%length(&prefix))-1);
+
+  %do x = 0 %to &maxtries;
+    %if %sysfunc(libref(&prefix&x)) ne 0 %then %do;
+      &prefix&x
+      %return;
+    %end;
+    %let x = %eval(&x + 1);
   %end;
-  %put unable to find available libref in range &prefix.0-&maxtries;
+
+  %put NOTE: Unable to find a usable libref in the range &prefix.0-&maxtries..;
+  %put NOTE: Change the prefix parameter.;
 %mend mf_getuniquelibref;
\ No newline at end of file