Slice

struct Slice

Represents a slice expression.

Objects of this type are generated when slice syntax is used within square brackets, for example:

var lst: List[Int] = [0, 1, 2, 3, 4, 5, 6, 7]

# Both produce the same new list: [6, 7].
var l1 = List(lst[6:])
var l2 = lst.__getitem__(Slice(6, len(lst)))

Fields

• ​start (Optional[Int]): The starting index of the slice.
• ​end (Optional[Int]): The end index of the slice.
• ​step (Optional[Int]): The step increment value of the slice.

Implemented traits

AnyType, Copyable, Deinitable, Equatable, ImplicitlyCopyable, Movable, Writable

Methods

__init__

def __init__(out self, start: Int, end: Int)

Constructs a slice with the given start and end bounds.

Args:

• ​start (Int): The starting index of the slice.
• ​end (Int): The end index of the slice.

def __init__(out self, start: Optional[Int], end: Optional[Int], step: Optional[Int], __slice_literal__: NoneType = None)

Constructs a slice with the given start, end, and step values.

Args:

• ​start (Optional[Int]): The starting index of the slice.
• ​end (Optional[Int]): The end index of the slice.
• ​step (Optional[Int]): The step increment value of the slice.
• ​slice_literal (NoneType): Enables slice literal syntax.

__eq__

def __eq__(self, other: Self) -> Bool

Compare this slice to the other.

Args:

• ​other (Self): The slice to compare to.

Returns:

Bool: True if start, end, and step values of this slice match the corresponding values of the other slice and False otherwise.

write_to

def write_to(self, mut writer: T)

Writes the slice's string representation to a writer.

Args:

• ​writer (T): The object to write to.

write_repr_to

def write_repr_to(self, mut writer: T)

Writes the slice's debug representation to a writer.

Args:

• ​writer (T): The object to write to.

indices

def indices(self, length: Int) -> Tuple[Int, Int, Int]

Resolves the slice's bounds against the length of a container.

Uses the target container length to resolve negative, out-of-bounds, or None bounds.

A negative bound counts back from the end of the container:

var s = slice(0, -1, 1)
print(s.indices(5))  # (0, 4, 1)

A None bound becomes the start or the end of the container based on the direction of the step:

var s = slice(None, None, 1)
print(s.indices(5))  # (0, 5, 1)

An out-of-bounds bound is clamped to the nearest valid bound in the step's direction:

var s = slice(20)
print(s.indices(5))  # (0, 5, 1)

Args:

• ​length (Int): The length of the container the slice applies to.

Returns:

Tuple[Int, Int, Int]: A tuple of the resolved start, end, and step.