# Dictionary Types

Dictionaries have the form `{K: V}`, where `K` is the type of the key, and `V` is the type of the value. For example, a dictionary with `Int` keys and `Bool` values has type `{Int: Bool}`.

```
// Declare a constant that has type `{Int: Bool}`,
// a dictionary mapping integers to booleans.
//
let booleans = {
    1: true,
    0: false
}

// Declare a constant that has type `{Bool: Int}`,
// a dictionary mapping booleans to integers.
//
let integers = {
    true: 1,
    false: 0
}
```

Dictionary types are covariant in their key and value types. For example, `[Int: String]` is a subtype of `[AnyStruct: String]` and also a subtype of `[Int: AnyStruct]`. This is safe because dictionaries are value types and not reference types.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://max-daunarovich.gitbook.io/flow-network/introduction/values-and-types/dictionaries/dictionary-types.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.