Maps ​

Maps are hashmap. Maps a unique key value to a value.

Example to maps:

fn main() {
    let mut mymap: map[i8]str = {
        0: "CPU",
        1: "RAM",
        2: "GPU"
    }
    println(mymap)
}

The example above shows how a map is defined and its data-type representation. To describe a map, curly braces are opened after the data type. Each key-value pair is separated by a comma. Keys and values are separated by colons, the key comes first, then the value.

Access to Elements and Indexing ​

To get the value of a key, it is sufficient to index it with the key.

For example:

mymap[1]

The example at above, gives "RAM" value.
If you try to access a key that does not exist, it will return the default value.

To change the value of a key, it is sufficient to do a classic assignment by indexing the key.

For example:

mymap[1] = "SSD"

To add a key-value pair that doesn't exist, it's still just a classic assignment.

For example:

mymap[3] = "HDD"

If the key does not exist when you assign it, the key is generated and matched with the value you assigned.

Delete Keys ​

The built-in delete function deletes relevant key from map. Takes two argument, the first one is the map, second one is the key to delete.

For example:

fn main() {
    let mut myMap: map[int]str = {
        0: "Foo",
        1: "Bar",
        2: "FooBar"
    }
    delete(myMap, 2)
    println(len(m))
}

At the example above, the delete call will remove 2:"FooBar" pair from the map.

If you want remove all keys without deallocating internal buffer memory, just give the map without key.

For example:

fn main() {
    let mut myMap: map[int]str = {
        0: "Foo",
        1: "Bar",
        2: "FooBar"
    }
    delete(myMap, 2)
    println(len(m))
}

At the example above, the delete call will remove all keys of the map without deallocating buffer. It is efficient way to clear map for make ready to reuse or something like that.

Lookup Assignments ​

Lookup assignments are efficient way to lookup in hashmaps. They lookups for key, and assign value of key to relevant expression if found. The second assignment is report of whether key is found.

For example:

fn main() {
    let mut myMap: map[int]str = {
        0: "Foo",
        1: "Bar",
        2: "FooBar"
    }
    let (value, ok) = myMap[1]
    println(value)
    println(ok)
}

At the example above, variable value will assign to value of key if key found, leaving initialized with default value if not. The variable ok assign to true if key found, false if not.