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How I learned to love the struct and stop worrying (part I)...
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| /// Equatable operators - avoid boxing operands when comparing structs. | |
| /// Source: https://github.com/dotnet/fsharp/issues/526#issuecomment-119755563 | |
| module EquatableOperators = | |
| let inline eq<'a when 'a :> System.IEquatable<'a>> (x:'a) (y:'a) = x.Equals y | |
| let inline (==) x y = eq x y | |
| let inline (!=) x y = not (eq x y) | |
| /// We get a fair warning that it's odd that we impl. custom equality | |
| /// when we deny the equality operator. | |
| [<Struct; NoEquality; NoComparison>] | |
| type BoxAversePoint = | |
| { X: int | |
| Y: int } | |
| interface IEquatable<BoxAversePoint> with | |
| member x.Equals y = | |
| x.X = y.X && | |
| x.Y = y.Y | |
| let a = { X = 1; Y = 2 } | |
| let b = a | |
| let c = { X = -1; Y = -2 } | |
| // Do not (and now cannot - due to NoEquality) | |
| //do a = b |> ignore // boxes operands, structs allocate memory | |
| //do a = c |> ignore // boxes operands, structs allocate memory | |
| open EquatableOperators | |
| // Do | |
| do a == b |> ignore // no boxing | |
| do a == c |> ignore // no boxing |
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