os, filepath: reorganize functions

vlib/filepath/filepath.v

@@ -3,18 +3,16 @@ module filepath
 import (
 	os
 )
-// return the extension in the file `path`
-
 
+// ext returns the extension in the file `path`.
 pub fn ext(path string) string {
-	pos := path.last_index_byte(`.`)
-	if pos != -1 {
-		return path[pos..]
+	pos := path.last_index('.') or {
+		return ''
 	}
-	return ''
+	return path[pos..]
 }
 
-// returns true if `path` is absolute
+// is_abs returns true if `path` is absolute.
 pub fn is_abs(path string) bool {
 	$if windows {
 		return path[0] == `/` || // incase we're in MingGW bash
@@ -23,8 +21,7 @@ pub fn is_abs(path string) bool {
 	return path[0] == `/`
 }
 
-// pass directories as parameters, returns path as string
-// TODO use []string.join once ...string becomes "[]string"
+// join returns path as string from string parameter(s).
 pub fn join(base string, dirs ...string) string {
 	mut result := []string
 	result << base.trim_right('\\/')
@@ -34,3 +31,27 @@ pub fn join(base string, dirs ...string) string {
 	return result.join(os.path_separator)
 }
 
+// dir returns all but the last element of path, typically the path's directory.
+pub fn dir(path string) string {
+	if path == '.' {
+		return os.getwd()
+	}
+	pos := path.last_index(os.path_separator) or {
+		return '.'
+	}
+	return path[..pos]
+}
+
+// basedir returns a directory name from path
+pub fn basedir(path string) string {
+	pos := path.last_index(os.path_separator) or {
+		return path
+	}
+	// NB: *without* terminating /
+	return path[..pos]
+}
+
+// filename returns a file name from path
+pub fn filename(path string) string {
+	return path.all_after(os.path_separator)
+}