From 3522342c0ba70ac4768291596eb735889faf9992 Mon Sep 17 00:00:00 2001
From: Lucas Bajolet <r4pass@hotmail.com>
Date: Mon, 24 Mar 2014 13:01:20 -0400
Subject: [PATCH] stdlib/strings: Added reverse iterators on char views for
 Strings.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
---
 lib/standard/string.nit |   90 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)

diff --git a/lib/standard/string.nit b/lib/standard/string.nit
index 524d4d4..f33bc0b 100644
--- a/lib/standard/string.nit
+++ b/lib/standard/string.nit
@@ -380,8 +380,42 @@ abstract class StringCharView
 
 	redef fun iterator: IndexedIterator[Char] do return self.iterator_from(0)
 
+	# Gets a new Iterator starting at position `pos`
+	#
+	# Ex :
+	#	var iter = "abcd".iterator_from(2)
+	#	while iter.is_ok do
+	#		printn iter.item
+	#		iter.next
+	#	end
+	#
+	# Outputs : cd
 	fun iterator_from(pos: Int): IndexedIterator[Char] is abstract
 
+	# Gets an iterator starting at the end and going backwards
+	#
+	# Ex :
+	#	var reviter = "now step live...".reverse_iterator
+	#	while reviter.is_ok do
+	#		printn reviter.item
+	#		reviter.next
+	#	end
+	#
+	# Outputs : ...evil pets won
+	fun reverse_iterator: IndexedIterator[Char] do return self.reverse_iterator_from(self.length - 1)
+
+	# Gets an iterator on the chars of self starting from `pos`
+	#
+	# Ex :
+	#	var iter = "abcd".reverse_iterator_from(1)
+	#	while iter.is_ok do
+	#		printn iter.item
+	#		iter.next
+	#	end
+	#
+	# Outputs : ba
+	fun reverse_iterator_from(pos: Int): IndexedIterator[Char] is abstract
+
 	redef fun has(c: Char): Bool
 	do
 		for i in self do
@@ -711,6 +745,32 @@ class String
 	end
 end
 
+private class FlatStringReverseIterator
+	super IndexedIterator[Char]
+
+	var target: String
+
+	var target_items: NativeString
+
+	var curr_pos: Int
+
+	init with_pos(tgt: String, pos: Int)
+	do
+		target = tgt
+		target_items = tgt.items
+		curr_pos = pos + tgt.index_from
+	end
+
+	redef fun is_ok do return curr_pos >= 0
+
+	redef fun item do return target_items[curr_pos]
+
+	redef fun next do curr_pos -= 1
+
+	redef fun index do return curr_pos - target.index_from
+
+end
+
 private class FlatStringIterator
 	super IndexedIterator[Char]
 
@@ -753,6 +813,8 @@ private class FlatStringCharView
 
 	redef fun iterator_from(start) do return new FlatStringIterator.with_pos(target, start)
 
+	redef fun reverse_iterator_from(start) do return new FlatStringReverseIterator.with_pos(target, start)
+
 end
 
 # Mutable strings of characters.
@@ -882,6 +944,32 @@ class Buffer
 	readable private var _capacity: Int
 end
 
+private class FlatBufferReverseIterator
+	super IndexedIterator[Char]
+
+	var target: Buffer
+
+	var target_items: NativeString
+
+	var curr_pos: Int
+
+	init with_pos(tgt: Buffer, pos: Int)
+	do
+		target = tgt
+		target_items = tgt.items
+		curr_pos = pos
+	end
+
+	redef fun index do return curr_pos
+
+	redef fun is_ok do return curr_pos >= 0
+
+	redef fun item do return target_items[curr_pos]
+
+	redef fun next do curr_pos -= 1
+
+end
+
 private class FlatBufferCharView
 	super BufferCharView
 	super StringCapable
@@ -924,6 +1012,8 @@ private class FlatBufferCharView
 
 	redef fun iterator_from(pos) do return new FlatBufferIterator.with_pos(target, pos)
 
+	redef fun reverse_iterator_from(pos) do return new FlatBufferReverseIterator.with_pos(target, pos)
+
 end
 
 private class FlatBufferIterator
-- 
1.7.9.5