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|
list_new := ??{
x := {
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'");
}
y := nil;
if idx == 0 {
front {
y = value;
}
} else {
front {
get_helper(next, idx - 1) {y = x;}
}
}
x := y;
};
list_get = ??(list, idx){
if idx < 0 {
throw_error("Negative index in 'list_get'");
}
y := nil;
list {
get_helper(front, idx) {y = x;}
}
x := y;
};
};
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);
}
};
};
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