add root_name(), improve is_absolute implementation

Author: scivision

+stdlib/hostname.m

@@ -4,5 +4,11 @@
 % Ref: https://docs.oracle.com/javase/8/docs/api/java/net/InetAddress.html#getHostName--
 
 function name = hostname()
+
+if stdlib.isoctave
+  name = gethostname();
+else
   name = string(java.net.InetAddress.getLocalHost().getHostName());
 end
+
+end

+stdlib/is_absolute.m

@@ -1,20 +1,39 @@
 %% IS_ABSOLUTE is path absolute?
 %
-% Ref: https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/io/File.html#isAbsolute()
+%!assert(is_absolute('', false), false)
+%!test
+%! if ispc
+%!   assert(is_absolute('C:\', false), true)
+%!   assert(is_absolute('C:/', false), true)
+%!   assert(is_absolute('C:', false), false)
+%!   assert(is_absolute('C', false), false)
+%! else
+%!   assert(is_absolute('/', false), true)
+%!   assert(is_absolute('/usr', false), true)
+%!   assert(is_absolute('usr', false), false)
+%! endif
 
 function isabs = is_absolute(p, use_java)
 arguments
-  p (1,1) string
+  p (1,1)
   use_java (1,1) logical = false
 end
 
 if use_java
   % java is about 5x to 10x slower than intrinsic
+  % https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/io/File.html#isAbsolute()
   isabs = java.io.File(p).toPath().isAbsolute();
+elseif ischar(p)
+  L = length(p);
+  if ispc
+    isabs = L > 2 && ~isempty(stdlib.root_name(p)) && (p(3) == '\' || p(3) == '/');
+  else
+    isabs = L >= 1 && p(1) == '/';
+  end
 else
   L = strlength(p);
   if ispc
-    isabs = L >= 2 && isletter(extractBetween(p, 1, 1)) && extractBetween(p, 2, 2) == ":";
+    isabs = L > 2 && strlength(stdlib.root_name(p)) >= 2 && any(extractBetween(p, 3, 3) == ['/', '\']);
   else
     isabs = L >= 1 && startsWith(p, "/");
   end

+stdlib/is_exe.m

@@ -1,6 +1,8 @@
 %% IS_EXE is file executable
 %
-% Ref: https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/io/File.html#canExecute()
+% false if file does not exist
+%
+%!assert (is_exe('', false), false)
 
 function ok = is_exe(file, use_java)
 arguments
@@ -11,13 +13,14 @@
 if use_java
 % about the same time as fileattrib
 % doesn't need absolute path like other Java functions
+% https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/io/File.html#canExecute()
 ok = java.io.File(file).canExecute();
 
 % more complicated
 % ok = java.nio.file.Files.isExecutable(java.io.File(stdlib.canonical(file)).toPath());
 
 else
-  if strlength(file) == 0
+  if stdlib.len(file) == 0
     ok = false;
     return
   end

+stdlib/is_readable.m

@@ -1,6 +1,9 @@
 %% IS_READABLE is file readable
 %
 % Ref: https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/nio/file/Files.html#isReadable(java.nio.file.Path)
+%
+%!assert (is_readable('is_readable.m', false))
+%!assert (is_readable('', false), false)
 
 function ok = is_readable(file, use_java)
 arguments

+stdlib/is_writable.m

@@ -1,6 +1,7 @@
 %% IS_WRITABLE is path writable
 %
-% Ref: https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/nio/file/Files.html#isWritable(java.nio.file.Path)
+%!assert (is_writable('is_writable.m', false))
+%!assert (is_writable('', false), false)
 
 function ok = is_writable(file, use_java)
 arguments
@@ -13,6 +14,7 @@
   % needs absolute()
   file = stdlib.absolute(file, "", false, use_java);
 
+  % https://docs.oracle.com/en/java/javase/22/docs/api/java.base/java/nio/file/Files.html#isWritable(java.nio.file.Path)
   ok = java.nio.file.Files.isWritable(java.io.File(file).toPath());
 else
   [status, v] = fileattrib(file);

+stdlib/iscygwin.m

@@ -1,6 +1,7 @@
 %% ISCYGWIN  Detect if running under Cygwin
 
 function iscyg = iscygwin()
+
 if ispc || ismac
   iscyg = false;
 elseif isunix

+stdlib/isoctave.m

@@ -1,5 +1,13 @@
 %% ISOCTAVE Detects if this is GNU Octave
 
 function isoct = isoctave()
-isoct = exist('OCTAVE_VERSION', 'builtin') == 5;
+
+persistent o
+
+if isempty(o)
+  o = exist('OCTAVE_VERSION', 'builtin') == 5;
+end
+
+isoct = o;
+
 end

+stdlib/len.m

@@ -0,0 +1,11 @@
+function L = len(s)
+
+L = [];
+
+if ischar(s)
+  L = length(s);
+elseif isstring(s)
+  L = strlength(s);
+end
+
+end

+stdlib/parent.m

@@ -16,7 +16,7 @@
   % drop duplicated slashes in the parent path
   p = regexprep(p, "//+", "/");
 
-  if ispc && any(strlength(p) == [2,3]) && isletter(extractBetween(p, 1, 1)) && extractBetween(p, 2, 2) == ":"
+  if ispc && any(strlength(p) == [2,3]) && strlength(stdlib.root_name(p))
     % 2 or 3 char drive letter
     p = stdlib.root(p);
     return

+stdlib/posix.m

@@ -1,14 +1,16 @@
 %% POSIX posix format of path with '/' separator
 % convert a path to a Posix string path separated with "/" even on Windows.
 % If Windows path also have escaping "\" this breaks
+%
+%!assert (posix('/'), '/')
 
 function r = posix(p)
 arguments
-  p string
+  p (1,1) string
 end
 
 if ispc
-  r = strrep(p, "\", "/");
+  r = strrep(p, '\', '/');
 else
   r = p;
 end