# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1485732685 -3600
# Node ID c38bb702df65be751f2de0ed4e3ffae6b85d9b5b
# Parent  b2b0c13d325228f54533a1aebc5f0a3fd4f3ebff
Changed string and Unicode slicing methods with use of the generic sequence
slicing functionality, producing string/Unicode results. This is less efficient
than using the substring native functions, but it reduces code complexity.

diff -r b2b0c13d3252 -r c38bb702df65 lib/__builtins__/sequence.py
--- a/lib/__builtins__/sequence.py	Sun Jan 29 22:56:43 2017 +0100
+++ b/lib/__builtins__/sequence.py	Mon Jan 30 00:31:25 2017 +0100
@@ -36,22 +36,6 @@
         if index < 0 or index >= self.__len__():
             raise IndexError(index)
 
-    def _confine_index(self, index):
-
-        """
-        Return the given absolute 'index', confined by the bounds of the
-        sequence.
-        """
-
-        length = self.__len__()
-
-        if index < 0:
-            return 0
-        elif index > length:
-            return length
-        else:
-            return index
-
     def __getitem__(self, index):
 
         "Return the item or slice specified by 'index'."
@@ -153,9 +137,18 @@
 
     def __get_multiple_items__(self, start, end, step):
 
-        "Method to be overridden by subclasses."
+        """
+        Return items from 'start' until (but excluding) 'end', at 'step'
+        intervals.
+        """
 
-        return None
+        result = []
+
+        while step > 0 and start < end or step < 0 and start > end:
+            result.append(self.__get_single_item__(start))
+            start += step
+
+        return result
 
     def __len__(self):
 
@@ -283,21 +276,6 @@
 
         raise StopIteration()
 
-    def __get_multiple_items__(self, start, end, step):
-
-        """
-        Return items from 'start' until (but excluding) 'end', at 'step'
-        intervals.
-        """
-
-        result = []
-
-        while step > 0 and start < end or step < 0 and start > end:
-            result.append(self.__get_single_item__(start))
-            start += step
-
-        return result
-
 def _get_absolute_index(index, length):
 
     """
diff -r b2b0c13d3252 -r c38bb702df65 lib/__builtins__/str.py
--- a/lib/__builtins__/str.py	Sun Jan 29 22:56:43 2017 +0100
+++ b/lib/__builtins__/str.py	Mon Jan 30 00:31:25 2017 +0100
@@ -537,17 +537,16 @@
         intervals.
         """
 
-        start = self._confine_index(start)
-        end = self._confine_index(end)
+        if start == end:
+            return ""
+
         check_int(step)
 
         if step == 0:
             raise ValueError(step)
 
-        if start == end:
-            return ""
-
-        return str_substr(self.__data__, start, end, step)
+        l = get_using(basestring.__get_multiple_items__, self)(start, end, step)
+        return "".join(l)
 
 def str(obj):
 
diff -r b2b0c13d3252 -r c38bb702df65 lib/__builtins__/unicode.py
--- a/lib/__builtins__/unicode.py	Sun Jan 29 22:56:43 2017 +0100
+++ b/lib/__builtins__/unicode.py	Mon Jan 30 00:31:25 2017 +0100
@@ -179,17 +179,16 @@
         intervals.
         """
 
-        start = self._confine_index(start)
-        end = self._confine_index(end)
+        if start == end:
+            return ""
+
         check_int(step)
 
         if step == 0:
             raise ValueError(step)
 
-        if start == end:
-            return ""
-
-        return utf8string(unicode_substr(self.__data__, start, end, step), self.encoding)
+        l = get_using(basestring.__get_multiple_items__, self)(start, end, step)
+        return utf8string("".join(l), self.encoding)
 
 def unicode(s, encoding):