Problems encountered during Sturct packing

Problems encountered during Sturct packing

An Object will generate a temporary variable in the stack space during unpacking. Therefore, it is better to declare all content as readonly when using Struct.

[<Struct>] type Point = val mutable X: double val mutable Y: double member x. change (a, B) = x. X <-a x. Y <-B override x. toString () = sprintf "% A" x. X x. ylet mutable p = Point (X = 1 ., Y = 1 .) p. toString () // out: 1.0 1.0p.Change (3 ., 2 .) p. toString () // out: 3.0 2.0let o = p:> objo. toString () // out: 3.0 2.0 (o:?> Point). Change (5., 5.) o. ToString () // no change out: 3.0 2.0

F # The generated struct instance is read-only by default. That is to say, without mutable, Change does not work at all. Better protection.