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Version: 1.0.0
For the complete Mojo documentation index, see llms.txt. Markdown versions of all pages are available by appending .md to any URL (e.g. /docs/manual/basics.md).

TypeDict

struct TypeDict[T: Equatable & Movable, Trait: AnyTrait[AnyType], //, keys: List[T], *values: Trait]

A compile-time map from a value of type T to a type.

TypeDict pairs a list of compile-time key values with a list of types of the same length. Looking up a key value yields the type at the matching position, so it acts as a value-keyed switch over types resolved entirely at compile time.

Examples:

from std.collections import TypeDict
from std.testing import assert_equal

comptime td = TypeDict[
    T=Int,
    Trait=AnyType,
    [1,2,3],
    Int, String, Float64,
]

def main() raises:
    comptime assert td.get[1] == Int
    comptime assert td.get[2] == String
    comptime assert td.get[3] == Float64
    assert_equal(td.length, 3)

Parameters​

  • ​T (Equatable & Movable): The type of the key values.
  • ​Trait (AnyTrait[AnyType]): The trait that every mapped type conforms to.
  • ​keys (List[T]): The key values, one per mapped type.
  • ​*values (Trait): The mapped types, parallel to keys.

Implemented traits​

AnyType, Copyable, Deinitable, ImplicitlyCopyable, Movable, RegisterPassable, TrivialRegisterPassable

comptime members​

get​

comptime get[key: T] = values[SIMDLength(keys.try_index(key, Int(0), Optional(None)).or_else(TypeDict._assert_key_is_present[key]()))]

Gets the type mapped to key.

Constraints: key must be present in keys.

Parameters​

  • ​key (T): The key value to look up.

length​

comptime length = len[TypeList[values]](values)

The number of entries in the map.

Methods​

__init__​

def __init__() -> Self

Constructs a TypeDict.

Constraints:

keys and values must have the same length.

__len__​

def __len__(self) -> Int

Gets the number of entries in the map.

Returns:

Int: The number of entries in the map (length).

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