Optional

Optional type. Also known as a Maybe or Option type in some languages.

This can either contain a value or be none. It works with any value, including values that can be null. I.e. null is a valid value that can be contained inside an optional if T is a pointer type

It also has range like behavior. So this acts as a range that contains 1 element or is empty. Similar to std.algorithm.only

And all operations that can be performed on a T can also be performed on an Optional!T. The behavior of applying an operation on a no-value or null pointer is well defined and safe.

struct Optional (

) {

enum bool isMutable(T); via import std.traits : isMutable, isSomeFunction, isAssignable, Unqual;;

enum bool isSomeFunction(alias T); via import std.traits : isMutable, isSomeFunction, isAssignable, Unqual;;

eponymoustemplate isAssignable(Lhs, Rhs = Lhs) via import std.traits : isMutable, isSomeFunction, isAssignable, Unqual;;

alias Unqual = CoreUnqual via import std.traits : isMutable, isSomeFunction, isAssignable, Unqual;;

static Optional!T construct(Args args);

this(U value);

this(None );

bool empty [@property getter];

inout(T) front [@property getter];

void popFront();

bool opEquals(None );

bool opEquals(Optional!U rhs);

bool opEquals(U rhs);

bool opEquals(R other);

void opAssign(None );

void opAssign(U lhs);

void opAssign(Optional!U lhs);

auto ref opUnary();

auto ref opBinary(U rhs);

auto ref opBinaryRight(U lhs);

auto ref opCall(Args args);

auto ref opOpAssign(U rhs);

static if(from!"std.traits".isArray!T)

auto ref opIndex();

static if(from!"std.traits".isArray!T)

auto opDollar();

}

Constructors

this this(U value)
this(None ): Constructs an Optional!T value by assigning T

Members

Functions

opAssign void opAssign(None )
void opAssign(U lhs)
void opAssign(Optional!U lhs): Assigns a value to the optional or sets it to none.
opBinary auto ref opBinary(U rhs): If the optional is some value it returns an optional of some value op rhs
opBinaryRight auto ref opBinaryRight(U lhs): If the optional is some value it returns an optional of some lhs op value
opCall auto ref opCall(Args args): If there's a value that's callable it will be called else it's a noop
opDollar auto opDollar(): Ditto Ditto
opEquals bool opEquals(None )
bool opEquals(Optional!U rhs)
bool opEquals(U rhs)
bool opEquals(R other): Compare two optionals or an optional with some value
opIndex auto ref opIndex(): Provides indexing into arrays
opOpAssign auto ref opOpAssign(U rhs): If the optional is some value, op assigns rhs to it
opUnary auto ref opUnary(): Applies unary operator to internal value of optional.
popFront void popFront(): Undocumented in source. Be warned that the author may not have intended to support it.

Properties

empty bool empty [@property getter]: Undocumented in source. Be warned that the author may not have intended to support it.
front inout(T) front [@property getter]: Undocumented in source. Be warned that the author may not have intended to support it.

Static functions

construct Optional!T construct(Args args): Allows you to create an Optional type in place.