# Maps

**`0x1::simple_map`**

This module provides a solution for sorted maps, that is it has the properties that

* Keys point to Values
* Each Key must be unique
* A Key can be found within O(Log N) time
* The data is stored as sorted by Key
* Adds and removals take O(N) time

**Defining an empty map:**

```rust
let NAME : SimpleMap<TYPE1,TYPE2> = simple_map::create();
```

**Operations on maps:**

Lets understand various *operations* on maps using the module given below.

```rust
module my_addrx::Mapping
{
    use std::simple_map::{SimpleMap,Self};
    use std::string::{String,utf8};

    public fun mapping_in_move()
    {
        let mp:SimpleMap<u64,String> = simple_map::create(); //creating an empty map where Key->integer and Value->string.
        
        
        //adding the key and corresponding value in the map
        simple_map::add(&mut mp,1 ,utf8(b"John")); 
        simple_map::add(&mut mp,2 ,utf8(b"Ben"));
        simple_map::add(&mut mp,3 ,utf8(b"Tony"));
        simple_map::add(&mut mp,4 ,utf8(b"Gwen"));
      
        //calculating the length of the map
        let l=simple_map::length(&mut mp);
        assert!(l==4,1);

        //checking if a given key exists or not in the vector
        let x=simple_map::contains_key(&mut mp,&2);
        assert!(x==true,1);

        //removing key value pair in the map
        simple_map::remove(&mut mp,&2);
        assert!(simple_map::contains_key(&mut mp,&2)==false,1);

        //borrowing immutable reference to the value of a given key        
        let v=simple_map::borrow(&mut mp,&3);
        assert!(v==&utf8(b"Tony"),1);

        //borrowing mutable reference to the value of a given key        
        let v=simple_map::borrow_mut(&mut mp,&3);
        *v=utf8(b"Changed Name");
        
        assert!(simple_map::borrow(&mut mp,&3)==&utf8(b"Changed Name"),1);


    }

    #[test]
    fun testing()
    {
        mapping_in_move();
    }
}t
```

{% hint style="info" %}
For more information on maps follow [this link.](https://github.com/aptos-labs/aptos-core/blob/mainnet/aptos-move/framework/aptos-stdlib/doc/simple_map.md#@Specification_1_create)
{% endhint %}


---

# 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://move-developers-dao.gitbook.io/aptos-move-by-example/intermediate-concepts/maps.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.