F# Enumeration

Enumerations in F# are a user-defined type that allows you to define a set of named constant values. An enumeration can be defined using the enum keyword.

Syntax

The syntax for defining an enumeration in F# is as follows:

type enumTypeName =
    | Value1 = value1
    | Value2 = value2
    | Value3 = value3
    ...

• enumTypeName is the name of the enumeration type
• Value1, Value2, Value3 are the named constants of the enumeration
• value1, value2, value3 are the integer values associated with the named constants

Example

type Color =
    | Red = 1
    | Green = 2
    | Blue = 3

let color = Color.Red
printfn "%A" color

Output

Red

Explanation

In the example above, we have defined an enumeration type named Color with three named constants: Red, Green, and Blue. The integer values associated with each of the named constants are 1, 2, and 3 respectively.

We then declare a variable color of type Color and assign it the value Color.Red. When we print the value of color using printfn, it prints the name of the named constant Red.

Use

Enumerations are primarily used to improve code readability and maintainability. Instead of representing values using integers or strings, we can use meaningful named constants.

Enumerations are also useful in switch statements and pattern matching expressions to handle different cases.

Important Points

• Enumeration values are 32-bit integers by default
• You can explicitly set the integer value of an enumeration value
• The order in which the named constants are defined determines their integer value. The first constant has a value of 0, the second has a value of 1, and so on.

Summary

In F#, you can define an enumeration type using the enum keyword. Enumerations are a useful way to define a set of named constants that improve code readability and maintainability. They are primarily used in switch statements and pattern matching expressions to handle different cases.