drop_slash: simplify and add tests

Author: scivision

+stdlib/drop_slash.m

@@ -8,25 +8,16 @@
   p {mustBeTextScalar}
 end
 
-s = stdlib.posix(p);
-
-uncslash = ispc() && startsWith(s, '//');
-
 % drop repeated slashes inside string
-d = regexprep(s, '/+', '/');
-
-L = strlength(d);
+d = regexprep(char(p), '/+', '/');
 
-if L < 2
-  if uncslash
-    d = '//';
-  end
-elseif ~ispc() || (L ~= 3 || ~strcmp(d, stdlib.root(s)))
-  d = regexprep(d, '/$', '');
+% drop trailing slash "/" or "\", but preserve a single slash if that's the only character
+while strlength(d) > 1 && endsWith(d, {'/', '\'})
+  d = d(1:end-1);
 end
 
-if uncslash
-  d = strcat('/', d);
+if ispc() && ~isempty(d) && strcmp(d, stdlib.root_name(p))
+  d = strcat(d, '/');
 end
 
 if isstring(p)

test/TestNormalize.m

@@ -2,12 +2,18 @@
 
 properties (TestParameter)
 p = init_norm()
+d = init_drop_slash()
 end
 
 methods (Test)
 function test_normalize(tc, p)
 tc.verifyEqual(stdlib.normalize(p{1}), p{2})
 end
+
+function test_drop_slash(tc, d)
+tc.verifyEqual(stdlib.drop_slash(d{1}), d{2})
+end
+
 end
 
 end
@@ -38,3 +44,27 @@ function test_normalize(tc, p)
   p{3}{2} = "//a/b";
 end
 end
+
+
+function d = init_drop_slash()
+d = {...
+{"", ""}, ...
+{'a', 'a'}, ...
+{"a/", "a"}, ...
+{"a/b", "a/b"}, ...
+{"a/b/", "a/b"}, ...
+{"////", "/"}, ...
+{"a////b", "a/b"}, ...
+{"a//b//", "a/b"}, ...
+{"///", "/"}, ...
+{'/', '/'}};
+if ispc()
+  dd = {...
+    {"c:/", "c:/"}, ...
+    {"c://", "c:/"}, ...
+    {"c:///a/b//", "c:/a/b"}, ...
+    {"c:/a/b//", "c:/a/b"}
+  };
+  d = [d, dd];
+end
+end