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struct

Variant

A runtime-variant type.

Data for this type is stored internally. Currently, its size is the largest size of any of its variants plus a 16-bit discriminant.

You can - use isa[T]() to check what type a variant is - use take[T]() to take a value from the variant - use get[T]() to get a value out of a variant - This currently does an extra copy/move until we have lifetimes - It also temporarily requires the value to be mutable - use set[T](owned new_value: T) to reset the variant to a new value

Example:

from utils import Variant
alias IntOrString = Variant[Int, String]
fn to_string(inout x: IntOrString) -> String:
    if x.isa[String]():
        return x.get[String]()[]
    # x.isa[Int]()
    return str(x.get[Int]()[])

# They have to be mutable for now, and implement CollectionElement
var an_int = IntOrString(4)
var a_string = IntOrString(String("I'm a string!"))
var who_knows = IntOrString(0)
import random
if random.random_ui64(0, 1):
    who_knows.set[String]("I'm actually a string too!")

print(to_string(an_int))
print(to_string(a_string))
print(to_string(who_knows))

Parameters​

  • ​*Ts (CollectionElement): The elements of the variadic.

Implemented traits​

AnyType, CollectionElement, Copyable, Movable

Methods​

__init__​

__init__[T: CollectionElement](inout self: Self, /, owned value: T)

Create a variant with one of the types.

Parameters:

  • ​T (CollectionElement): The type to initialize the variant to. Generally this should be able to be inferred from the call type, eg. Variant[Int, String](4).

Args:

  • ​value (T): The value to initialize the variant with.

__copyinit__​

__copyinit__(inout self: Self, /, other: Self)

Creates a deep copy of an existing variant.

Args:

  • ​other (Self): The variant to copy from.

__moveinit__​

__moveinit__(inout self: Self, /, owned other: Self)

Move initializer for the variant.

Args:

  • ​other (Self): The variant to move.

__del__​

__del__(owned self: Self)

Destroy the variant.

take​

take[T: CollectionElement](owned self: Self) -> $0

Take the current value of the variant as the provided type.

The caller takes ownership of the underlying value. The variant type is consumed without calling any deleters.

This doesn't explicitly check that your value is of that type! If you haven't verified the type correctness at runtime, you'll get a type that looks like your type, but has potentially unsafe and garbage member data.

Parameters:

  • ​T (CollectionElement): The type to take.

Returns:

The undelying data as an owned value.

set​

set[T: CollectionElement](inout self: Self, owned value: T)

Set the variant value.

This will call the destructor on the old value, and update the variant's internal type and data to the new value.

Parameters:

  • ​T (CollectionElement): The new variant type. Must be one of the Variant's type arguments.

Args:

  • ​value (T): The new value to set the variant to.

isa​

isa[T: CollectionElement](self: Self) -> Bool

Check if the variant contains the required type.

Parameters:

  • ​T (CollectionElement): The type to check.

Returns:

True if the variant contains the requested type.

get​

get[T: CollectionElement, mutability: i1, self_life: lifetime<*(0,1)>](self: !lit.ref<_stdlib::_utils::_variant::_Variant<:variadic<trait<_stdlib::_builtin::_value::_CollectionElement>> Ts>, mut=mutability, self_life>) -> Reference[$0, $1, $2, 0]

Get the value out of the variant as a type-checked type.

This doesn't explicitly check that your value is of that type! If you haven't verified the type correctness at runtime, you'll get a type that looks like your type, but has potentially unsafe and garbage member data.

For now this has the limitations that it - requires the variant value to be mutable

Parameters:

  • ​T (CollectionElement): The type of the value to get out.
  • ​mutability (i1): The inferred mutability of the variant type.
  • ​self_life (lifetime<*(0,1)>): The inferred lifetime of the variant type.

Returns:

The internal data represented as a Reference[T].