is_prefix: handle empty case

Author: scivision

+stdlib/is_prefix.m

@@ -11,7 +11,9 @@
 pr = stdlib.drop_slash(prefix);
 p = stdlib.drop_slash(pth);
 
-s = startsWith(p, pr) && (stdlib.len(p) >= stdlib.len(pr));
+Lp = stdlib.len(p);
+
+s = Lp && startsWith(p, pr) && (Lp >= stdlib.len(pr));
 
 end
 

test/TestIsSubdir.m

@@ -9,11 +9,13 @@
 methods (Test)
 
 function test_is_subdir(tc, p_is_subdir)
-tc.verifyEqual(stdlib.is_subdir(p_is_subdir{1}, p_is_subdir{2}), p_is_subdir{3}, "subdir(" + p_is_subdir{1} + "," + p_is_subdir{2} + ")")
+tc.verifyEqual(stdlib.is_subdir(p_is_subdir{1}, p_is_subdir{2}), p_is_subdir{3}, ...
+  "subdir(" + p_is_subdir{1} + "," + p_is_subdir{2} + ")")
 end
 
 function test_is_prefix(tc, p_is_prefix)
-tc.verifyEqual(stdlib.is_prefix(p_is_prefix{1}, p_is_prefix{2}), p_is_prefix{3}, "prefix(" + p_is_prefix{1} + "," + p_is_prefix{2} + ")")
+tc.verifyEqual(stdlib.is_prefix(p_is_prefix{1}, p_is_prefix{2}), p_is_prefix{3}, ...
+  "prefix(" + p_is_prefix{1} + "," + p_is_prefix{2} + ")")
 end
 
 end
@@ -31,7 +33,9 @@ function test_is_prefix(tc, p_is_prefix)
     {"a/b/c", "a/./b", false}, ...
     {"a/b", "a/b/", false}, ...
     {"a/b", "a", true}, ...
-    {"a/.c", "a", true}
+    {"a/.c", "a", true}, ...
+    {"file:///", "file:///", false}, ...
+    {"", "", false}, ...
 };
 % NOTE: ".." in is_subdir (either argument) is ambiguous
 
@@ -50,5 +54,5 @@ function test_is_prefix(tc, p_is_prefix)
 p{6}{3} = true;
 p{7}{3} = false;
 p{8}{3} = false;
-p{9}{3} = true;
+p{11}{3} = true;
 end