Value types

Regular tuple/record/union are reference-types by default, but it's possible to get them as value-types

• Instances stored on the Stack rather than in the Heap

• Records, Unions: [<Struct>] attribute

• Tuples, Anonymous Records: struct keyword

Struct tuples & anonymous records

// Struct tuple
let a = struct (1, 'b', "Three") // struct (int * char * string)

// Struct anonymous record
let b = struct {| Num = 1; Char = 'b'; Text = "Three" |}

Struct records & unions

// Struct record
[<Struct>]
type Point = { X: float; Y: float }
let p = { X = 1.0; Y = 2.3 } // val p: Point = { X = 1.0; Y = 2.3 }

// Struct union: unique fields labels are required❗
[<Struct>]
type Multicase =
    | Int  of i: int
    | Char of c: char
    | Text of s: string
let t = Int 1 // val t: Multicase = Int 1

⚖️ Pros/Cons

• ✅ Efficient because no garbage collection

• ⚠️ Passed by value → memory pressure

Recommendations:

Consider structs for small types with high allocation rates

🔗 F# coding conventions / Performance