option.md

Module 0x1::option

This module defines the Option type and its methods to represent and handle an optional value.

• Struct Option
• Constants
• Function none
• Function some
• Function from_vec
• Function is_none
• Function is_some
• Function contains
• Function borrow
• Function borrow_with_default
• Function get_with_default
• Function fill
• Function extract
• Function borrow_mut
• Function swap
• Function swap_or_fill
• Function destroy_with_default
• Function destroy_some
• Function destroy_none
• Function to_vec
• Function for_each
• Function for_each_ref
• Function for_each_mut
• Function fold
• Function map
• Function map_ref
• Function filter
• Function any
• Function destroy
• Module Specification

use 0x1::vector;

Struct Option

Abstraction of a value that may or may not be present. Implemented with a vector of size zero or one because Move bytecode does not have ADTs.

struct Option<Element> has copy, drop, store

Constants

The Option is in an invalid state for the operation attempted. The Option is Some while it should be None.

const EOPTION_IS_SET: u64 = 262144;

The Option is in an invalid state for the operation attempted. The Option is None while it should be Some.

const EOPTION_NOT_SET: u64 = 262145;

Cannot construct an option from a vector with 2 or more elements.

const EOPTION_VEC_TOO_LONG: u64 = 262146;

Function none

Return an empty Option

public fun none<Element>(): option::Option<Element>

Function some

Return an Option containing e

public fun some<Element>(e: Element): option::Option<Element>

Function from_vec

public fun from_vec<Element>(vec: vector<Element>): option::Option<Element>

Function is_none

Return true if t does not hold a value

public fun is_none<Element>(t: &option::Option<Element>): bool

Function is_some

Return true if t holds a value

public fun is_some<Element>(t: &option::Option<Element>): bool

Function contains

Return true if the value in t is equal to e_ref Always returns false if t does not hold a value

public fun contains<Element>(t: &option::Option<Element>, e_ref: &Element): bool

Function borrow

Return an immutable reference to the value inside t Aborts if t does not hold a value

public fun borrow<Element>(t: &option::Option<Element>): &Element

Function borrow_with_default

Return a reference to the value inside t if it holds one Return default_ref if t does not hold a value

public fun borrow_with_default<Element>(t: &option::Option<Element>, default_ref: &Element): &Element

Function get_with_default

Return the value inside t if it holds one Return default if t does not hold a value

public fun get_with_default<Element: copy, drop>(t: &option::Option<Element>, default: Element): Element

Function fill

Convert the none option t to a some option by adding e. Aborts if t already holds a value

public fun fill<Element>(t: &mut option::Option<Element>, e: Element)

Function extract

Convert a some option to a none by removing and returning the value stored inside t Aborts if t does not hold a value

public fun extract<Element>(t: &mut option::Option<Element>): Element

Function borrow_mut

Return a mutable reference to the value inside t Aborts if t does not hold a value

public fun borrow_mut<Element>(t: &mut option::Option<Element>): &mut Element

Function swap

Swap the old value inside t with e and return the old value Aborts if t does not hold a value

public fun swap<Element>(t: &mut option::Option<Element>, e: Element): Element

Function swap_or_fill

Swap the old value inside t with e and return the old value; or if there is no old value, fill it with e. Different from swap(), swap_or_fill() allows for t not holding a value.

public fun swap_or_fill<Element>(t: &mut option::Option<Element>, e: Element): option::Option<Element>

Function destroy_with_default

Destroys t. If t holds a value, return it. Returns default otherwise

public fun destroy_with_default<Element: drop>(t: option::Option<Element>, default: Element): Element

Function destroy_some

Unpack t and return its contents Aborts if t does not hold a value

public fun destroy_some<Element>(t: option::Option<Element>): Element

Function destroy_none

Unpack t Aborts if t holds a value

public fun destroy_none<Element>(t: option::Option<Element>)

Function to_vec

Convert t into a vector of length 1 if it is Some, and an empty vector otherwise

public fun to_vec<Element>(t: option::Option<Element>): vector<Element>

Function for_each

Apply the function to the optional element, consuming it. Does nothing if no value present.

public fun for_each<Element>(o: option::Option<Element>, f: |Element|())

Function for_each_ref

Apply the function to the optional element reference. Does nothing if no value present.

public fun for_each_ref<Element>(o: &option::Option<Element>, f: |&Element|())

Function for_each_mut

Apply the function to the optional element reference. Does nothing if no value present.

public fun for_each_mut<Element>(o: &mut option::Option<Element>, f: |&mut Element|())

Function fold

Folds the function over the optional element.

public fun fold<Accumulator, Element>(o: option::Option<Element>, init: Accumulator, f: |(Accumulator, Element)|Accumulator): Accumulator

Function map

Maps the content of an option.

public fun map<Element, OtherElement>(o: option::Option<Element>, f: |Element|OtherElement): option::Option<OtherElement>

Function map_ref

Maps the content of an option without destroying the original option.

public fun map_ref<Element, OtherElement>(o: &option::Option<Element>, f: |&Element|OtherElement): option::Option<OtherElement>

Function filter

Filters the content of an option

public fun filter<Element: drop>(o: option::Option<Element>, f: |&Element|bool): option::Option<Element>

Function any

Returns true if the option contains an element which satisfies predicate.

public fun any<Element>(o: &option::Option<Element>, p: |&Element|bool): bool

Function destroy

Utility function to destroy an option that is not droppable.

public fun destroy<Element>(o: option::Option<Element>, d: |Element|())

Module Specification