root_name: improve correctness

Author: scivision

+stdlib/root_name.m

@@ -10,16 +10,16 @@
   p {mustBeTextScalar}
 end
 
-r = "";
+r = '';
 
 if ~ispc || strlength(p) < 2
-  return
-end
-
-c = char(p);
+  % noop
+else
+  c = char(p);
 
-if c(2) == ':' && isletter(c(1))
-  r = c(1:2);
+  if c(2) == ':' && isletter(c(1))
+    r = c(1:2);
+  end
 end
 
 if isstring(p)

test/TestFilePure.m

@@ -36,7 +36,7 @@ function test_root_name(tc, p)
 
 p = {{"", ""}, ...
 {"a/b", ""}, ...
-{"/etc", ""}, ...
+{'/etc', ''}, ...
 {"c:/etc", ""}
 };
 

test/TestFilename.m

@@ -2,10 +2,11 @@
 
 properties (TestParameter)
 p = {
+{'', ''}, ...
 {"", ""}, ...
 {"/a/b/c", "c"}, ...
-{"/a/b/c/", ""}, ...
-{"a/b/c.txt", "c.txt"}, ...
+{'/a/b/c/', ''}, ...
+{'a/b/c.txt', 'c.txt'}, ...
 {"a/b/c.txt.gz", "c.txt.gz"}, ...
 };
 end