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|
new_list := ??{
front := nil
back := nil
}
list_push_front := ??(list, item){
list {
if front == nil {
front = {
value := item
next := nil
prev := nil
}
back = front
} else {
front = {
value := item
next := front
prev := nil
}
}
}
}
list_push_back := ??(list, item){
list {
if back == nil {
front = {
value := item
next := nil
prev := nil
}
back = front
} else {
back = {
value := item
next := nil
prev := back
}
}
}
}
list_pop_front := ??(list){
x := nil
list {
if front == nil {
throw_error("Call to 'list_pop_front' on empty list")
}
front {
x = value
front = next
}
if front == nil {
back = nil
}
}
}
list_pop_back := ??(list){
x := nil
list {
if back == nil {
throw_error("Call to 'list_pop_back' on empty list")
}
back {
x = value
back = prev
}
if back == nil {
front = nil
}
}
}
list_get := nil
{
get_helper := ??(front, idx){
if front == nil {
throw_error("Index past end of list in 'list_get'")
}
x := nil
if idx == 0 {
front {
x = value
}
} else {
front {
found := nil
get_helper(next, idx - 1){
found = x
}
x = found
}
}
}
list_get = ??(list, idx){
if idx < 0 {
throw_error("Negative index in 'list_get'")
}
x := nil
list {
found := nil
get_helper(front, idx){
found = x
}
x = found
}
}
}
list_set := nil
{
set_helper := ??(front, idx, val){
if front == nil {
throw_error("Index past end of list in 'list_set'")
}
if idx == 0 {
front {
value = val
}
} else {
front {
set_helper(next, idx - 1, val){}
}
}
}
list_set = ??(list, idx, val){
if idx < 0 {
throw_error("Negative index in 'list_set'")
}
list {
set_helper(front, idx, val)
}
}
}
|
