union.fsx

#nowarn "9"

open System.Runtime.InteropServices

[<Struct; StructLayout(LayoutKind.Explicit)>]
type s =
    [<DefaultValue; FieldOffset 0>]
    val mutable y : uint32
    [<DefaultValue; FieldOffset 0>]
    val mutable x1 : byte
    [<DefaultValue; FieldOffset 1>]
    val mutable x2 : byte
    [<DefaultValue; FieldOffset 2>]
    val mutable x3 : byte
    [<DefaultValue; FieldOffset 3>]
    val mutable x4 : byte

do
    let t  = s(x1 = 1uy, x2 = 2uy, x3 = 3uy, x4 = 4uy)
    printfn "%x" t.y
do
    let t  = s(y = 0x01020304u)
    printfn "%x %x %x %x" t.x1 t.x2 t.x3 t.x4