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Doubly-linked list/Traversal: Difference between revisions
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=={{header|Fortran}}==
see [[Doubly-linked list/Definition#Fortran]]
=={{header|Go}}==
Code is identical to that for task Doubly-linked list/Element insertion except for addition of section at the end of main noted "traverse from end to beginning." Traversal from beginning to end is adequately demonstrated by the String method of dlList.
Also note that there is a doubly linked list in the Go standard library in package container/list.
<lang go>package main
import "fmt"
type dlNode struct {
string
next, prev *dlNode
}
type dlList struct {
head, tail *dlNode
}
func (list *dlList) String() string {
if list.head == nil {
return fmt.Sprint(list.head)
}
r := "[" + list.head.string
for p := list.head.next; p != nil; p = p.next {
r += " " + p.string
}
return r + "]"
}
func (list *dlList) insertTail(node *dlNode) {
if list.tail == nil {
list.head = node
} else {
list.tail.next = node
}
node.next = nil
node.prev = list.tail
list.tail = node
}
func (list *dlList) insertAfter(existing, insert *dlNode) {
insert.prev = existing
insert.next = existing.next
existing.next.prev = insert
existing.next = insert
if existing == list.tail {
list.tail = insert
}
}
func main() {
dll := &dlList{}
fmt.Println(dll)
a := &dlNode{string: "A"}
dll.insertTail(a)
dll.insertTail(&dlNode{string: "B"})
fmt.Println(dll)
dll.insertAfter(a, &dlNode{string: "C"})
fmt.Println(dll)
// traverse from end to beginning
fmt.Print("From tail:")
for p := dll.tail; p != nil; p = p.prev {
fmt.Print(" ", p.string)
}
fmt.Println("")
}</lang>
Output:
<pre>
<nil>
[A B]
[A C B]
From tail: B C A
</pre>
=={{header|Haskell}}==
<lang haskell>main = print . traverse True $ create [10,20,30,40]
data DList a = Leaf | Node { prev::(DList a), elt::a, next::(DList a) }
create = go Leaf
where go _ [] = Leaf
go prev (x:xs) = current
where current = Node prev x next
next = go current xs
isLeaf Leaf = True
isLeaf _ = False
lastNode Leaf = Leaf
lastNode dl = until (isLeaf.next) next dl
traverse _ Leaf = []
traverse True (Node l v Leaf) = v : v : traverse False l
traverse dir (Node l v r) = v : traverse dir (if dir then r else l)</lang>
==Icon and {{header|Unicon}}==
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10</pre>
Uses the <code>print()</code> function from [[Rhino]] or [[SpiderMonkey]].
=={{header|Liberty BASIC}}==
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