F# - Mutable Dictionary

The Dictionary<'TKey, 'TValue> class is the mutable analog of the F# map data structure and contains many of the same functions.

Recapitulating from the Map chapter in F#, a map is a special kind of set that associates the values with key.

Creating of a Mutable Dictionary

Mutable dictionaries are created using the new keyword and calling the list's constructor. The following example demonstrates this −

open System.Collections.Generic
let dict = new Dictionary<string, string>()
dict.Add("1501", "Zara Ali")
dict.Add("1502","Rishita Gupta")
dict.Add("1503","Robin Sahoo")
dict.Add("1504","Gillian Megan")
printfn "Dictionary - students: %A" dict

When you compile and execute the program, it yields the following output −

Dictionary - students: seq
[[1501, Zara Ali]; [1502, Rishita Gupta]; [1503, Robin Sahoo];
[1504, Gillian Megan]]

The Dictionary(TKey,TValue) Class

The Dictionary(TKey, TValue) Class represents a collection of keys and values.

The following tables provide the properties, constructors and the methods of the List(T) class −

Properties

Constructors

Methods

Example

open System.Collections.Generic
let dict = new Dictionary<string, string>()

dict.Add("1501", "Zara Ali")
dict.Add("1502","Rishita Gupta")
dict.Add("1503","Robin Sahoo")
dict.Add("1504","Gillian Megan")

printfn "Dictionary - students: %A" dict
printfn "Total Number of Students: %d" dict.Count
printfn "The keys: %A" dict.Keys
printf"The Values: %A" dict.Values

When you compile and execute the program, it yields the following output −

Dictionary - students: seq
[[1501, Zara Ali]; [1502, Rishita Gupta]; [1503, Robin Sahoo];
[1504, Gillian Megan]]
Total Number of Students: 4
The keys: seq ["1501"; "1502"; "1503"; "1504"]
The Values: seq ["Zara Ali"; "Rishita Gupta"; "Robin Sahoo"; "Gillian Megan"]