Buffer

Class Buffer<X> provides a mutable list of elements of type X. The class wraps and resizes an underyling array that holds the elements, and thus is comparable to ArrayLists or Vectors in other languages.

When required, the current state of a buffer object can be converted to a fixed-size array of its elements. This is recommended for example when storing a buffer to a stable variable.

Throughout this documentation, two terms come up that can be confused: size and capacity. size is the length of the list that the buffer represents. capacity is the length of the underyling array that backs this list. capacity >= size is an invariant for this class.

Like arrays, elements in the buffer are ordered by indices from 0 to size-1.

WARNING: Certain operations are amortized O(1) time, such as add, but run in worst case O(n) time. These worst case runtimes may exceed the cycles limit per message if the size of the buffer is large enough. Grow these structures with discretion. All amortized operations below also list the worst case runtime.

Constructor: The argument initCapacity determines the initial capacity of the array. The underlying array grows by a factor of 1.5 when its current capacity is exceeded. Further, when the size of the buffer shrinks to be less than 1/4th of the capacity, the underyling array is shrunk by a factor of 2.

Example:

import Buffer "mo:base/Buffer";

let buffer = Buffer.Buffer<Nat>(3); // Creates a new Buffer

Runtime: O(initCapacity)

Space: O(initCapacity)

Class Buffer<X>

class Buffer<X>(initCapacity : Nat)

Function size

func size() : Nat

Returns the current number of elements in the buffer.

Example:

buffer.size() // => 0

Runtime: O(1)

Space: O(1)

Function add

func add(element : X)

Adds a single element to the end of the buffer, doubling the size of the array if capacity is exceeded.

Example:

buffer.add(0); // add 0 to buffer
buffer.add(1);
buffer.add(2);
buffer.add(3); // causes underlying array to increase in capacity
Buffer.toArray(buffer) // => [0, 1, 2, 3]

Amortized Runtime: O(1), Worst Case Runtime: O(size)

Amortized Space: O(1), Worst Case Space: O(size)

Function get

func get(index : Nat) : X

Returns the element at index index. Traps if index >= size. Indexing is zero-based.

Example:

buffer.add(10);
buffer.add(11);
buffer.get(0); // => 10

Runtime: O(1)

Space: O(1)

Function getOpt

func getOpt(index : Nat) : ?X

Returns the element at index index as an option. Returns null when index >= size. Indexing is zero-based.

Example:

buffer.add(10);
buffer.add(11);
let x = buffer.getOpt(0); // => ?10
let y = buffer.getOpt(2); // => null

Runtime: O(1)

Space: O(1)

Function put

func put(index : Nat, element : X)

Overwrites the current element at index with element. Traps if index >= size. Indexing is zero-based.

Example:

buffer.add(10);
buffer.put(0, 20); // overwrites 10 at index 0 with 20
Buffer.toArray(buffer) // => [20]

Runtime: O(1)

Space: O(1)

Function removeLast

func removeLast() : ?X

Removes and returns the last item in the buffer or null if the buffer is empty.

Example:

buffer.add(10);
buffer.add(11);
buffer.removeLast(); // => ?11

Amortized Runtime: O(1), Worst Case Runtime: O(size)

Amortized Space: O(1), Worst Case Space: O(size)

Function remove

func remove(index : Nat) : X

Removes and returns the element at index from the buffer. All elements with index > index are shifted one position to the left. This may cause a downsizing of the array.

Traps if index >= size.

WARNING: Repeated removal of elements using this method is ineffecient and might be a sign that you should consider a different data-structure for your use case.

Example:

buffer.add(10);
buffer.add(11);
buffer.add(12);
let x = buffer.remove(1); // evaluates to 11. 11 no longer in list.
Buffer.toArray(buffer) // => [10, 12]

Runtime: O(size)

Amortized Space: O(1), Worst Case Space: O(size)

Function clear

func clear()

Resets the buffer. Capacity is set to 8.

Example:

buffer.add(10);
buffer.add(11);
buffer.add(12);
buffer.clear(); // buffer is now empty
Buffer.toArray(buffer) // => []

Runtime: O(1)

Space: O(1)

Function filterEntries

func filterEntries(predicate : (Nat, X) -> Bool)

Removes all elements from the buffer for which the predicate returns false. The predicate is given both the index of the element and the element itself. This may cause a downsizing of the array.

Example:

buffer.add(10);
buffer.add(11);
buffer.add(12);
buffer.filterEntries(func(_, x) = x % 2 == 0); // only keep even elements
Buffer.toArray(buffer) // => [10, 12]

Runtime: O(size)

Amortized Space: O(1), Worst Case Space: O(size)

Function capacity

func capacity() : Nat

Returns the capacity of the buffer (the length of the underlying array).

Example:

let buffer = Buffer.Buffer<Nat>(2); // underlying array has capacity 2
buffer.add(10);
let c1 = buffer.capacity(); // => 2
buffer.add(11);
buffer.add(12); // causes capacity to increase by factor of 1.5
let c2 = buffer.capacity(); // => 3

Runtime: O(1)

Space: O(1)

Function reserve

func reserve(capacity : Nat)

Changes the capacity to capacity. Traps if capacity < size.

buffer.reserve(4);
buffer.add(10);
buffer.add(11);
buffer.capacity(); // => 4

Runtime: O(capacity)

Space: O(capacity)

Function append

func append(buffer2 : Buffer<X>)

Adds all elements in buffer b to this buffer.

let buffer1 = Buffer.Buffer<Nat>(2);
let buffer2 = Buffer.Buffer<Nat>(2);
buffer1.add(10);
buffer1.add(11);
buffer2.add(12);
buffer2.add(13);
buffer1.append(buffer2); // adds elements from buffer2 to buffer1
Buffer.toArray(buffer1) // => [10, 11, 12, 13]

Amortized Runtime: O(size2), Worst Case Runtime: O(size1 + size2)

Amortized Space: O(1), Worst Case Space: O(size1 + size2)

Function insert

func insert(index : Nat, element : X)

Inserts element at index, shifts all elements to the right of index over by one index. Traps if index is greater than size.

let buffer1 = Buffer.Buffer<Nat>(2);
let buffer2 = Buffer.Buffer<Nat>(2);
buffer.add(10);
buffer.add(11);
buffer.insert(1, 9);
Buffer.toArray(buffer) // => [10, 9, 11]

Runtime: O(size)

Amortized Space: O(1), Worst Case Space: O(size)

Function insertBuffer

func insertBuffer(index : Nat, buffer2 : Buffer<X>)

Inserts buffer2 at index, and shifts all elements to the right of index over by size2. Traps if index is greater than size.

let buffer1 = Buffer.Buffer<Nat>(2);
let buffer2 = Buffer.Buffer<Nat>(2);
buffer1.add(10);
buffer1.add(11);
buffer2.add(12);
buffer2.add(13);
buffer1.insertBuffer(1, buffer2);
Buffer.toArray(buffer1) // => [10, 12, 13, 11]

Runtime: O(size)

Amortized Space: O(1), Worst Case Space: O(size1 + size2)

Function sort

func sort(compare : (X, X) -> Order.Order)

Sorts the elements in the buffer according to compare. Sort is deterministic, stable, and in-place.

import Nat "mo:base/Nat";

buffer.add(11);
buffer.add(12);
buffer.add(10);
buffer.sort(Nat.compare);
Buffer.toArray(buffer) // => [10, 11, 12]

Runtime: O(size * log(size))

Space: O(size)

Function vals

func vals() : { next : () -> ?X }

Returns an Iterator (Iter) over the elements of this buffer. Iterator provides a single method next(), which returns elements in order, or null when out of elements to iterate over.

buffer.add(10);
buffer.add(11);
buffer.add(12);

var sum = 0;
for (element in buffer.vals()) {
  sum += element;
};
sum // => 33

Runtime: O(1)

Space: O(1)

Function clone

func clone() : Buffer<X>

@deprecated Use static library function instead.

Function toArray

func toArray() : [X]

@deprecated Use static library function instead.

Function toVarArray

func toVarArray() : [var X]

@deprecated Use static library function instead.

Function isEmpty

func isEmpty<X>(buffer : Buffer<X>) : Bool

Returns true if and only if the buffer is empty.

Example:

buffer.add(2);
buffer.add(0);
buffer.add(3);
Buffer.isEmpty(buffer); // => false

Buffer.isEmpty(buffer); // => true

Runtime: O(1)

Space: O(1)

Function contains

func contains<X>(buffer : Buffer<X>, element : X, equal : (X, X) -> Bool) : Bool

Returns true iff buffer contains element with respect to equality defined by equal.

Example:

import Nat "mo:base/Nat";

buffer.add(2);
buffer.add(0);
buffer.add(3);
Buffer.contains<Nat>(buffer, 2, Nat.equal); // => true

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that equal runs in O(1) time and space.

Function clone

func clone<X>(buffer : Buffer<X>) : Buffer<X>

Returns a copy of buffer, with the same capacity.

Example:

buffer.add(1);

let clone = Buffer.clone(buffer);
Buffer.toArray(clone); // => [1]

Runtime: O(size)

Space: O(size)

Function max

func max<X>(buffer : Buffer<X>, compare : (X, X) -> Order) : ?X

Finds the greatest element in buffer defined by compare. Returns null if buffer is empty.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);

Buffer.max(buffer, Nat.compare); // => ?2

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that compare runs in O(1) time and space.

Function min

func min<X>(buffer : Buffer<X>, compare : (X, X) -> Order) : ?X

Finds the least element in buffer defined by compare. Returns null if buffer is empty.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);

Buffer.min(buffer, Nat.compare); // => ?1

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that compare runs in O(1) time and space.

Function equal

func equal<X>(buffer1 : Buffer<X>, buffer2 : Buffer<X>, equal : (X, X) -> Bool) : Bool

Defines equality for two buffers, using equal to recursively compare elements in the buffers. Returns true iff the two buffers are of the same size, and equal evaluates to true for every pair of elements in the two buffers of the same index.

Example:

import Nat "mo:base/Nat";

let buffer1 = Buffer.Buffer<Nat>(2);
buffer1.add(1);
buffer1.add(2);

let buffer2 = Buffer.Buffer<Nat>(5);
buffer2.add(1);
buffer2.add(2);

Buffer.equal(buffer1, buffer2, Nat.equal); // => true

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that equal runs in O(1) time and space.

Function compare

func compare<X>(buffer1 : Buffer<X>, buffer2 : Buffer<X>, compare : (X, X) -> Order.Order) : Order.Order

Defines comparison for two buffers, using compare to recursively compare elements in the buffers. Comparison is defined lexicographically.

Example:

import Nat "mo:base/Nat";

let buffer1 = Buffer.Buffer<Nat>(2);
buffer1.add(1);
buffer1.add(2);

let buffer2 = Buffer.Buffer<Nat>(3);
buffer2.add(3);
buffer2.add(4);

Buffer.compare<Nat>(buffer1, buffer2, Nat.compare); // => #less

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that compare runs in O(1) time and space.

Function toText

func toText<X>(buffer : Buffer<X>, toText : X -> Text) : Text

Creates a textual representation of buffer, using toText to recursively convert the elements into Text.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

Buffer.toText(buffer, Nat.toText); // => "[1, 2, 3, 4]"

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that toText runs in O(1) time and space.

Function hash

func hash<X>(buffer : Buffer<X>, hash : X -> Nat32) : Nat32

Hashes buffer using hash to hash the underlying elements. The deterministic hash function is a function of the elements in the Buffer, as well as their ordering.

Example:

import Hash "mo:base/Hash";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(1000);

Buffer.hash<Nat>(buffer, Hash.hash); // => 2_872_640_342

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that hash runs in O(1) time and space.

Function indexOf

func indexOf<X>(element : X, buffer : Buffer<X>, equal : (X, X) -> Bool) : ?Nat

Finds the first index of element in buffer using equality of elements defined by equal. Returns null if element is not found.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

Buffer.indexOf<Nat>(3, buffer, Nat.equal); // => ?2

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that equal runs in O(1) time and space.

Function lastIndexOf

func lastIndexOf<X>(element : X, buffer : Buffer<X>, equal : (X, X) -> Bool) : ?Nat

Finds the last index of element in buffer using equality of elements defined by equal. Returns null if element is not found.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);
buffer.add(2);
buffer.add(2);

Buffer.lastIndexOf<Nat>(2, buffer, Nat.equal); // => ?5

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that equal runs in O(1) time and space.

Function indexOfBuffer

func indexOfBuffer<X>(subBuffer : Buffer<X>, buffer : Buffer<X>, equal : (X, X) -> Bool) : ?Nat

Searches for subBuffer in buffer, and returns the starting index if it is found.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);
buffer.add(5);
buffer.add(6);

let sub = Buffer.Buffer<Nat>(2);
sub.add(4);
sub.add(5);
sub.add(6);

Buffer.indexOfBuffer<Nat>(sub, buffer, Nat.equal); // => ?3

Runtime: O(size of buffer + size of subBuffer)

Space: O(size of subBuffer)

*Runtime and space assumes that equal runs in O(1) time and space.

Function binarySearch

func binarySearch<X>(element : X, buffer : Buffer<X>, compare : (X, X) -> Order.Order) : ?Nat

Similar to indexOf, but runs in logarithmic time. Assumes that buffer is sorted. Behavior is undefined if buffer is not sorted. Uses compare to perform the search. Returns an index of element if it is found.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(4);
buffer.add(5);
buffer.add(6);

Buffer.binarySearch<Nat>(5, buffer, Nat.compare); // => ?2

Runtime: O(log(size))

Space: O(1)

*Runtime and space assumes that compare runs in O(1) time and space.

Function subBuffer

func subBuffer<X>(buffer : Buffer<X>, start : Nat, length : Nat) : Buffer<X>

Returns the sub-buffer of buffer starting at index start of length length. Traps if start is out of bounds, or start + length is greater than the size of buffer.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);
buffer.add(5);
buffer.add(6);

let sub = Buffer.subBuffer(buffer, 3, 2);
Buffer.toText(sub, Nat.toText); // => [4, 5]

Runtime: O(length)

Space: O(length)

Function isSubBufferOf

func isSubBufferOf<X>(subBuffer : Buffer<X>, buffer : Buffer<X>, equal : (X, X) -> Bool) : Bool

Checks if subBuffer is a sub-Buffer of buffer. Uses equal to compare elements.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);
buffer.add(5);
buffer.add(6);

let sub = Buffer.Buffer<Nat>(2);
sub.add(2);
sub.add(3);
Buffer.isSubBufferOf(sub, buffer, Nat.equal); // => true

Runtime: O(size of subBuffer + size of buffer)

Space: O(size of subBuffer)

*Runtime and space assumes that equal runs in O(1) time and space.

Function isStrictSubBufferOf

func isStrictSubBufferOf<X>(subBuffer : Buffer<X>, buffer : Buffer<X>, equal : (X, X) -> Bool) : Bool

Checks if subBuffer is a strict subBuffer of buffer, i.e. subBuffer must be strictly contained inside both the first and last indices of buffer. Uses equal to compare elements.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

let sub = Buffer.Buffer<Nat>(2);
sub.add(2);
sub.add(3);
Buffer.isStrictSubBufferOf(sub, buffer, Nat.equal); // => true

Runtime: O(size of subBuffer + size of buffer)

Space: O(size of subBuffer)

*Runtime and space assumes that equal runs in O(1) time and space.

Function prefix

func prefix<X>(buffer : Buffer<X>, length : Nat) : Buffer<X>

Returns the prefix of buffer of length length. Traps if length is greater than the size of buffer.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

let pre = Buffer.prefix(buffer, 3); // => [1, 2, 3]
Buffer.toText(pre, Nat.toText);

Runtime: O(length)

Space: O(length)

Function isPrefixOf

func isPrefixOf<X>(prefix : Buffer<X>, buffer : Buffer<X>, equal : (X, X) -> Bool) : Bool

Checks if prefix is a prefix of buffer. Uses equal to compare elements.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

let pre = Buffer.Buffer<Nat>(2);
pre.add(1);
pre.add(2);
Buffer.isPrefixOf(pre, buffer, Nat.equal); // => true

Runtime: O(size of prefix)

Space: O(size of prefix)

*Runtime and space assumes that equal runs in O(1) time and space.

Function isStrictPrefixOf

func isStrictPrefixOf<X>(prefix : Buffer<X>, buffer : Buffer<X>, equal : (X, X) -> Bool) : Bool

Checks if prefix is a strict prefix of buffer. Uses equal to compare elements.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

let pre = Buffer.Buffer<Nat>(3);
pre.add(1);
pre.add(2);
pre.add(3);
Buffer.isStrictPrefixOf(pre, buffer, Nat.equal); // => true

Runtime: O(size of prefix)

Space: O(size of prefix)

*Runtime and space assumes that equal runs in O(1) time and space.

Function suffix

func suffix<X>(buffer : Buffer<X>, length : Nat) : Buffer<X>

Returns the suffix of buffer of length length. Traps if lengthis greater than the size of buffer.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

let suf = Buffer.suffix(buffer, 3); // => [2, 3, 4]
Buffer.toText(suf, Nat.toText);

Runtime: O(length)

Space: O(length)

Function isSuffixOf

func isSuffixOf<X>(suffix : Buffer<X>, buffer : Buffer<X>, equal : (X, X) -> Bool) : Bool

Checks if suffix is a suffix of buffer. Uses equal to compare elements.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

let suf = Buffer.Buffer<Nat>(3);
suf.add(2);
suf.add(3);
suf.add(4);
Buffer.isSuffixOf(suf, buffer, Nat.equal); // => true

Runtime: O(length of suffix)

Space: O(length of suffix)

*Runtime and space assumes that equal runs in O(1) time and space.

Function isStrictSuffixOf

func isStrictSuffixOf<X>(suffix : Buffer<X>, buffer : Buffer<X>, equal : (X, X) -> Bool) : Bool

Checks if suffix is a strict suffix of buffer. Uses equal to compare elements.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);

let suf = Buffer.Buffer<Nat>(3);
suf.add(2);
suf.add(3);
suf.add(4);
Buffer.isStrictSuffixOf(suf, buffer, Nat.equal); // => true

Runtime: O(length of suffix)

Space: O(length of suffix)

*Runtime and space assumes that equal runs in O(1) time and space.

Function forAll

func forAll<X>(buffer : Buffer<X>, predicate : X -> Bool) : Bool

Returns true iff every element in buffer satisfies predicate.

Example:

buffer.add(2);
buffer.add(3);
buffer.add(4);

Buffer.forAll<Nat>(buffer, func x { x > 1 }); // => true

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that predicate runs in O(1) time and space.

Function forSome

func forSome<X>(buffer : Buffer<X>, predicate : X -> Bool) : Bool

Returns true iff some element in buffer satisfies predicate.

Example:

buffer.add(2);
buffer.add(3);
buffer.add(4);

Buffer.forSome<Nat>(buffer, func x { x > 3 }); // => true

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that predicate runs in O(1) time and space.

Function forNone

func forNone<X>(buffer : Buffer<X>, predicate : X -> Bool) : Bool

Returns true iff no element in buffer satisfies predicate.

Example:

buffer.add(2);
buffer.add(3);
buffer.add(4);

Buffer.forNone<Nat>(buffer, func x { x == 0 }); // => true

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that predicate runs in O(1) time and space.

Function toArray

func toArray<X>(buffer : Buffer<X>) : [X]

Creates an array containing elements from buffer.

Example:

buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.toArray<Nat>(buffer); // => [1, 2, 3]

Runtime: O(size)

Space: O(size)

Function toVarArray

func toVarArray<X>(buffer : Buffer<X>) : [var X]

Creates a mutable array containing elements from buffer.

Example:

buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.toVarArray<Nat>(buffer); // => [1, 2, 3]

Runtime: O(size)

Space: O(size)

Function fromArray

func fromArray<X>(array : [X]) : Buffer<X>

Creates a buffer containing elements from array.

Example:

import Nat "mo:base/Nat";

let array = [2, 3];

let buf = Buffer.fromArray<Nat>(array); // => [2, 3]
Buffer.toText(buf, Nat.toText);

Runtime: O(size)

Space: O(size)

Function fromVarArray

func fromVarArray<X>(array : [var X]) : Buffer<X>

Creates a buffer containing elements from array.

Example:

import Nat "mo:base/Nat";

let array = [var 1, 2, 3];

let buf = Buffer.fromVarArray<Nat>(array); // => [1, 2, 3]
Buffer.toText(buf, Nat.toText);

Runtime: O(size)

Space: O(size)

Function fromIter

func fromIter<X>(iter : { next : () -> ?X }) : Buffer<X>

Creates a buffer containing elements from iter.

Example:

import Nat "mo:base/Nat";

let array = [1, 1, 1];
let iter = array.vals();

let buf = Buffer.fromIter<Nat>(iter); // => [1, 1, 1]
Buffer.toText(buf, Nat.toText);

Runtime: O(size)

Space: O(size)

Function trimToSize

func trimToSize<X>(buffer : Buffer<X>)

Reallocates the array underlying buffer such that capacity == size.

Example:

let buffer = Buffer.Buffer<Nat>(10);
buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.trimToSize<Nat>(buffer);
buffer.capacity(); // => 3

Runtime: O(size)

Space: O(size)

Function map

func map<X, Y>(buffer : Buffer<X>, f : X -> Y) : Buffer<Y>

Creates a new buffer by applying f to each element in buffer.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

let newBuf = Buffer.map<Nat, Nat>(buffer, func (x) { x + 1 });
Buffer.toText(newBuf, Nat.toText); // => [2, 3, 4]

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that f runs in O(1) time and space.

Function iterate

func iterate<X>(buffer : Buffer<X>, f : X -> ())

Applies f to each element in buffer.

Example:

import Nat "mo:base/Nat";
import Debug "mo:base/Debug";

buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.iterate<Nat>(buffer, func (x) {
  Debug.print(Nat.toText(x)); // prints each element in buffer
});

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that f runs in O(1) time and space.

Function mapEntries

func mapEntries<X, Y>(buffer : Buffer<X>, f : (Nat, X) -> Y) : Buffer<Y>

Applies f to each element in buffer and its index.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

let newBuf = Buffer.mapEntries<Nat, Nat>(buffer, func (x, i) { x + i + 1 });
Buffer.toText(newBuf, Nat.toText); // => [2, 4, 6]

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that f runs in O(1) time and space.

Function mapFilter

func mapFilter<X, Y>(buffer : Buffer<X>, f : X -> ?Y) : Buffer<Y>

Creates a new buffer by applying f to each element in buffer, and keeping all non-null elements.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

let newBuf = Buffer.mapFilter<Nat, Nat>(buffer, func (x) {
  if (x > 1) {
    ?(x * 2);
  } else {
    null;
  }
});
Buffer.toText(newBuf, Nat.toText); // => [4, 6]

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that f runs in O(1) time and space.

Function mapResult

func mapResult<X, Y, E>(buffer : Buffer<X>, f : X -> Result.Result<Y, E>) : Result.Result<Buffer<Y>, E>

Creates a new buffer by applying f to each element in buffer. If any invocation of f produces an #err, returns an #err. Otherwise Returns an #ok containing the new buffer.

Example:

import Result "mo:base/Result";

buffer.add(1);
buffer.add(2);
buffer.add(3);

let result = Buffer.mapResult<Nat, Nat, Text>(buffer, func (k) {
  if (k > 0) {
    #ok(k);
  } else {
    #err("One or more elements are zero.");
  }
});

Result.mapOk<Buffer.Buffer<Nat>, [Nat], Text>(result, func buffer = Buffer.toArray(buffer)) // => #ok([1, 2, 3])

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that f runs in O(1) time and space.

Function chain

func chain<X, Y>(buffer : Buffer<X>, k : X -> Buffer<Y>) : Buffer<Y>

Creates a new buffer by applying k to each element in buffer, and concatenating the resulting buffers in order. This operation is similar to what in other functional languages is known as monadic bind.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

let chain = Buffer.chain<Nat, Nat>(buffer, func (x) {
  let b = Buffer.Buffer<Nat>(2);
  b.add(x);
  b.add(x * 2);
  return b;
});
Buffer.toText(chain, Nat.toText); // => [1, 2, 2, 4, 3, 6]

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that k runs in O(1) time and space.

Function foldLeft

func foldLeft<A, X>(buffer : Buffer<X>, base : A, combine : (A, X) -> A) : A

Collapses the elements in buffer into a single value by starting with base and progessively combining elements into base with combine. Iteration runs left to right.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.foldLeft<Text, Nat>(buffer, "", func (acc, x) { acc # Nat.toText(x)}); // => "123"

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that combine runs in O(1) time and space.

Function foldRight

func foldRight<X, A>(buffer : Buffer<X>, base : A, combine : (X, A) -> A) : A

Collapses the elements in buffer into a single value by starting with base and progessively combining elements into base with combine. Iteration runs right to left.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.foldRight<Nat, Text>(buffer, "", func (x, acc) { Nat.toText(x) # acc }); // => "123"

Runtime: O(size)

Space: O(1)

*Runtime and space assumes that combine runs in O(1) time and space.

Function first

func first<X>(buffer : Buffer<X>) : X

Returns the first element of buffer. Traps if buffer is empty.

Example:

buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.first(buffer); // => 1

Runtime: O(1)

Space: O(1)

Function last

func last<X>(buffer : Buffer<X>) : X

Returns the last element of buffer. Traps if buffer is empty.

Example:

buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.last(buffer); // => 3

Runtime: O(1)

Space: O(1)

Function make

func make<X>(element : X) : Buffer<X>

Returns a new buffer with capacity and size 1, containing element.

Example:

import Nat "mo:base/Nat";

let buffer = Buffer.make<Nat>(1);
Buffer.toText(buffer, Nat.toText); // => [1]

Runtime: O(1)

Space: O(1)

Function reverse

func reverse<X>(buffer : Buffer<X>)

Reverses the order of elements in buffer.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.reverse(buffer);
Buffer.toText(buffer, Nat.toText); // => [3, 2, 1]

Runtime: O(size)

Space: O(1)

Function merge

func merge<X>(buffer1 : Buffer<X>, buffer2 : Buffer<X>, compare : (X, X) -> Order) : Buffer<X>

Merges two sorted buffers into a single sorted buffer, using compare to define the ordering. The final ordering is stable. Behavior is undefined if either buffer1 or buffer2 is not sorted.

Example:

import Nat "mo:base/Nat";

let buffer1 = Buffer.Buffer<Nat>(2);
buffer1.add(1);
buffer1.add(2);
buffer1.add(4);

let buffer2 = Buffer.Buffer<Nat>(2);
buffer2.add(2);
buffer2.add(4);
buffer2.add(6);

let merged = Buffer.merge<Nat>(buffer1, buffer2, Nat.compare);
Buffer.toText(merged, Nat.toText); // => [1, 2, 2, 4, 4, 6]

Runtime: O(size1 + size2)

Space: O(size1 + size2)

*Runtime and space assumes that compare runs in O(1) time and space.

Function removeDuplicates

func removeDuplicates<X>(buffer : Buffer<X>, compare : (X, X) -> Order)

Eliminates all duplicate elements in buffer as defined by compare. Elimination is stable with respect to the original ordering of the elements.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(1);
buffer.add(2);
buffer.add(3);

Buffer.removeDuplicates<Nat>(buffer, Nat.compare);
Buffer.toText(buffer, Nat.toText); // => [1, 2, 3]

Runtime: O(size * log(size))

Space: O(size)

Function partition

func partition<X>(buffer : Buffer<X>, predicate : X -> Bool) : (Buffer<X>, Buffer<X>)

Splits buffer into a pair of buffers where all elements in the left buffer satisfy predicate and all elements in the right buffer do not.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);
buffer.add(5);
buffer.add(6);

let partitions = Buffer.partition<Nat>(buffer, func (x) { x % 2 == 0 });
(Buffer.toArray(partitions.0), Buffer.toArray(partitions.1)) // => ([2, 4, 6], [1, 3, 5])

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that predicate runs in O(1) time and space.

Function split

func split<X>(buffer : Buffer<X>, index : Nat) : (Buffer<X>, Buffer<X>)

Splits the buffer into two buffers at index, where the left buffer contains all elements with indices less than index, and the right buffer contains all elements with indices greater than or equal to index. Traps if index is out of bounds.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);
buffer.add(5);
buffer.add(6);

let split = Buffer.split<Nat>(buffer, 3);
(Buffer.toArray(split.0), Buffer.toArray(split.1)) // => ([1, 2, 3], [4, 5, 6])

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that compare runs in O(1) time and space.

Function chunk

func chunk<X>(buffer : Buffer<X>, size : Nat) : Buffer<Buffer<X>>

Breaks up buffer into buffers of size size. The last chunk may have less than size elements if the number of elements is not divisible by the chunk size.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);
buffer.add(4);
buffer.add(5);
buffer.add(6);

let chunks = Buffer.chunk<Nat>(buffer, 3);
Buffer.toText<Buffer.Buffer<Nat>>(chunks, func buf = Buffer.toText(buf, Nat.toText)); // => [[1, 2, 3], [4, 5, 6]]

Runtime: O(number of elements in buffer)

Space: O(number of elements in buffer)

Function groupBy

func groupBy<X>(buffer : Buffer<X>, equal : (X, X) -> Bool) : Buffer<Buffer<X>>

Groups equal and adjacent elements in the list into sub lists.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(2);
buffer.add(4);
buffer.add(5);
buffer.add(5);

let grouped = Buffer.groupBy<Nat>(buffer, func (x, y) { x == y });
Buffer.toText<Buffer.Buffer<Nat>>(grouped, func buf = Buffer.toText(buf, Nat.toText)); // => [[1], [2, 2], [4], [5, 5]]

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that equal runs in O(1) time and space.

Function flatten

func flatten<X>(buffer : Buffer<Buffer<X>>) : Buffer<X>

Flattens the buffer of buffers into a single buffer.

Example:

import Nat "mo:base/Nat";

let buffer = Buffer.Buffer<Buffer.Buffer<Nat>>(1);

let inner1 = Buffer.Buffer<Nat>(2);
inner1.add(1);
inner1.add(2);

let inner2 = Buffer.Buffer<Nat>(2);
inner2.add(3);
inner2.add(4);

buffer.add(inner1);
buffer.add(inner2);
// buffer = [[1, 2], [3, 4]]

let flat = Buffer.flatten<Nat>(buffer);
Buffer.toText<Nat>(flat, Nat.toText); // => [1, 2, 3, 4]

Runtime: O(number of elements in buffer)

Space: O(number of elements in buffer)

Function zip

func zip<X, Y>(buffer1 : Buffer<X>, buffer2 : Buffer<Y>) : Buffer<(X, Y)>

Combines the two buffers into a single buffer of pairs, pairing together elements with the same index. If one buffer is longer than the other, the remaining elements from the longer buffer are not included.

Example:

let buffer1 = Buffer.Buffer<Nat>(2);
buffer1.add(1);
buffer1.add(2);
buffer1.add(3);

let buffer2 = Buffer.Buffer<Nat>(2);
buffer2.add(4);
buffer2.add(5);

let zipped = Buffer.zip(buffer1, buffer2);
Buffer.toArray(zipped); // => [(1, 4), (2, 5)]

Runtime: O(min(size1, size2))

Space: O(min(size1, size2))

Function zipWith

func zipWith<X, Y, Z>(buffer1 : Buffer<X>, buffer2 : Buffer<Y>, zip : (X, Y) -> Z) : Buffer<Z>

Combines the two buffers into a single buffer, pairing together elements with the same index and combining them using zip. If one buffer is longer than the other, the remaining elements from the longer buffer are not included.

Example:

let buffer1 = Buffer.Buffer<Nat>(2);
buffer1.add(1);
buffer1.add(2);
buffer1.add(3);

let buffer2 = Buffer.Buffer<Nat>(2);
buffer2.add(4);
buffer2.add(5);
buffer2.add(6);

let zipped = Buffer.zipWith<Nat, Nat, Nat>(buffer1, buffer2, func (x, y) { x + y });
Buffer.toArray(zipped) // => [5, 7, 9]

Runtime: O(min(size1, size2))

Space: O(min(size1, size2))

*Runtime and space assumes that zip runs in O(1) time and space.

Function takeWhile

func takeWhile<X>(buffer : Buffer<X>, predicate : X -> Bool) : Buffer<X>

Creates a new buffer taking elements in order from buffer until predicate returns false.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

let newBuf = Buffer.takeWhile<Nat>(buffer, func (x) { x < 3 });
Buffer.toText(newBuf, Nat.toText); // => [1, 2]

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that predicate runs in O(1) time and space.

Function dropWhile

func dropWhile<X>(buffer : Buffer<X>, predicate : X -> Bool) : Buffer<X>

Creates a new buffer excluding elements in order from buffer until predicate returns false.

Example:

import Nat "mo:base/Nat";

buffer.add(1);
buffer.add(2);
buffer.add(3);

let newBuf = Buffer.dropWhile<Nat>(buffer, func x { x < 3 }); // => [3]
Buffer.toText(newBuf, Nat.toText);

Runtime: O(size)

Space: O(size)

*Runtime and space assumes that predicate runs in O(1) time and space.