feat: new mf_existfunction macro

base/mf_existfunction.sas

@@ -0,0 +1,33 @@
+/**
+  @file
+  @brief Checks if a function exists
+  @details Returns 1 if the function exists, else 0
+  Usage:
+
+      %put %mf_existfunction(CAT);
+      %put %mf_existfunction(DOG);
+
+  Full credit to [Bart](https://sasensei.com/user/305) for the vfunc pointer
+  and the tidy approach for pure macro data set filtering.
+  Check out his [SAS Packages](https://github.com/yabwon/SAS_PACKAGES)
+  framework!
+
+  @param [in] name (positional) - function name
+
+  @author Allan Bowe
+**/
+/** @cond */
+
+%macro mf_existfunction(name
+)/*/STORE SOURCE*/;
+
+  %local dsid rc exist;
+  %let dsid=%sysfunc(open(sashelp.vfunc(where=(fncname="%upcase(&name)"))));
+  %let exist = %sysfunc(fetch(&dsid, NOSET));
+  %let rc = %sysfunc(close(&dsid));
+
+  %sysevalf(0 = &exist)
+
+%mend mf_existfunction;
+
+/** @endcond */