- iterator end on reverse-iterable data structures

containers/iterator.go

@@ -85,21 +85,24 @@ type IteratorWithKey interface {
 // Prev() function to enable traversal in reverse
 //
 // Last() function to move the iterator to the last element.
+//
+// End() function to move the iterator past the last element (one-past-the-end).
 type ReverseIteratorWithIndex interface {
 	// Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
 	// If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
 	// Modifies the state of the iterator.
 	Prev() bool
 
+	// End moves the iterator past the last element (one-past-the-end).
+	// Call Prev() to fetch the last element if any.
+	End()
+
 	// Last moves the iterator to the last element and returns true if there was a last element in the container.
 	// If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
 	// Modifies the state of the iterator.
 	Last() bool
 
 	IteratorWithIndex
-	// Next() bool
-	// Value() interface{}
-	// Index() int
 }
 
 // ReverseIteratorWithKey is a stateful iterator for ordered containers whose elements are key value pairs.
@@ -115,13 +118,14 @@ type ReverseIteratorWithKey interface {
 	// Modifies the state of the iterator.
 	Prev() bool
 
+	// End moves the iterator past the last element (one-past-the-end).
+	// Call Prev() to fetch the last element if any.
+	End()
+
 	// Last moves the iterator to the last element and returns true if there was a last element in the container.
 	// If Last() returns true, then last element's key and value can be retrieved by Key() and Value().
 	// Modifies the state of the iterator.
 	Last() bool
 
 	IteratorWithKey
-	// Next() bool
-	// Value() interface{}
-	// Key() interface{}
 }

examples/main/iteratorwithindex.go

@@ -0,0 +1,55 @@
+/*
+Copyright (c) 2015, Emir Pasic
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+package main
+
+import (
+	"fmt"
+	"github.com/emirpasic/gods/sets/treeset"
+)
+
+// IteratorWithIndexExample to demonstrate basic usage of IteratorWithIndex
+//func IteratorWithIndexExample() {
+func main() {
+	set := treeset.NewWithIntComparator()
+	set.Add(1, 2, 3)
+
+	// Forward iteration
+	it := set.Iterator()
+	for it.Next() {
+		index, value := it.Index(), it.Value()
+		fmt.Println("Index: ", index, "Value: ", value)
+	}
+
+	// Backward iteration (reverse)
+	for it.Last(); ; {
+		index, value := it.Index(), it.Value()
+		fmt.Println("Index: ", index, "Value: ", value)
+		if !it.Prev() {
+			break
+		}
+	}
+}

lists/arraylist/arraylist.go

@@ -230,6 +230,12 @@ func (iterator *Iterator) Begin() {
 	iterator.index = -1
 }
 
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	iterator.index = iterator.list.size
+}
+
 // First moves the iterator to the first element and returns true if there was a first element in the container.
 // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
@@ -242,7 +248,7 @@ func (iterator *Iterator) First() bool {
 // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
 func (iterator *Iterator) Last() bool {
-	iterator.index = iterator.list.size
+	iterator.End()
 	return iterator.Prev()
 }
 

lists/doublylinkedlist/doublylinkedlist.go

@@ -370,6 +370,13 @@ func (iterator *Iterator) Begin() {
 	iterator.element = nil
 }
 
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	iterator.index = iterator.list.size
+	iterator.element = iterator.list.last
+}
+
 // First moves the iterator to the first element and returns true if there was a first element in the container.
 // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
@@ -382,8 +389,7 @@ func (iterator *Iterator) First() bool {
 // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
 func (iterator *Iterator) Last() bool {
-	iterator.index = iterator.list.size
+	iterator.End()
-	iterator.element = iterator.list.last
 	return iterator.Prev()
 }
 

maps/treemap/treemap.go

@@ -171,12 +171,17 @@ func (iterator *Iterator) Begin() {
 	iterator.iterator.Begin()
 }
 
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	iterator.iterator.End()
+}
+
 // First moves the iterator to the first element and returns true if there was a first element in the container.
 // If First() returns true, then first element's key and value can be retrieved by Key() and Value().
 // Modifies the state of the iterator
 func (iterator *Iterator) First() bool {
-	iterator.Begin()
+	return iterator.iterator.First()
-	return iterator.Next()
 }
 
 // Last moves the iterator to the last element and returns true if there was a last element in the container.

sets/treeset/treeset.go

@@ -158,6 +158,13 @@ func (iterator *Iterator) Begin() {
 	iterator.iterator.Begin()
 }
 
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	iterator.index = iterator.tree.Size()
+	iterator.iterator.End()
+}
+
 // First moves the iterator to the first element and returns true if there was a first element in the container.
 // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
@@ -170,7 +177,7 @@ func (iterator *Iterator) First() bool {
 // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
 func (iterator *Iterator) Last() bool {
-	iterator.index = iterator.tree.Size()
+	iterator.End()
 	return iterator.iterator.Last()
 }
 

stacks/arraystack/arraystack.go

@@ -149,6 +149,12 @@ func (iterator *Iterator) Begin() {
 	iterator.index = -1
 }
 
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	iterator.index = iterator.stack.Size()
+}
+
 // First moves the iterator to the first element and returns true if there was a first element in the container.
 // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
@@ -161,7 +167,7 @@ func (iterator *Iterator) First() bool {
 // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
 func (iterator *Iterator) Last() bool {
-	iterator.index = iterator.stack.Size()
+	iterator.End()
 	return iterator.Prev()
 }
 

trees/binaryheap/binaryheap.go

@@ -165,6 +165,12 @@ func (iterator *Iterator) Begin() {
 	iterator.index = -1
 }
 
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	iterator.index = iterator.heap.Size()
+}
+
 // First moves the iterator to the first element and returns true if there was a first element in the container.
 // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
@@ -177,7 +183,7 @@ func (iterator *Iterator) First() bool {
 // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
 // Modifies the state of the iterator.
 func (iterator *Iterator) Last() bool {
-	iterator.index = iterator.heap.Size()
+	iterator.End()
 	return iterator.Prev()
 }
 

trees/redblacktree/redblacktree.go

@@ -363,6 +363,13 @@ func (iterator *Iterator) Begin() {
 	iterator.node = nil
 }
 
+// End moves the iterator past the last element (one-past-the-end).
+// Call Prev() to fetch the last element if any.
+func (iterator *Iterator) End() {
+	right := iterator.tree.Right() // ugly hack (TODO: use flags)
+	iterator.node = &Node{Parent: right, Key: right.Key}
+}
+
 // First moves the iterator to the first element and returns true if there was a first element in the container.
 // If First() returns true, then first element's key and value can be retrieved by Key() and Value().
 // Modifies the state of the iterator
@@ -375,8 +382,8 @@ func (iterator *Iterator) First() bool {
 // If Last() returns true, then last element's key and value can be retrieved by Key() and Value().
 // Modifies the state of the iterator.
 func (iterator *Iterator) Last() bool {
-	iterator.node = iterator.tree.Right()
+	iterator.End()
-	return iterator.node != nil
+	return iterator.Prev()
 }
 
 // String returns a string representation of container