is_exe: reusable code and more robust

Author: scivision

+stdlib/is_exe.m

@@ -12,8 +12,7 @@
 i = isfile(p);
 
 if ispc()
-  pe = split(string(getenv("PATHEXT")), pathsep);
-  i = i & endsWith(stdlib.suffix(p(i)), pe, 'IgnoreCase', true);
+  i = i & has_windows_executable_suffix(p(i));
 end
 
 if ~any(i), return, end

+stdlib/private/has_windows_executable_suffix.m

@@ -0,0 +1,14 @@
+function i = has_windows_executable_suffix(p)
+arguments
+  p string
+end
+
+pec = getenv("PATHEXT");
+if isempty(pec)
+  pec = '.COM;.EXE;.BAT;.CMD;';
+end
+pe = split(string(pec), pathsep);
+
+i = endsWith(stdlib.suffix(p), pe, 'IgnoreCase', true);
+
+end