Question

I want to swap both references, is there a nice way make such a construct work ?

 let mutable sarlast = ref (Array.copy ar)
 let mutable sarcurr = ref (Array.copy ar)
 ... some code ...

 sarcurr, sarlast <- sarlast, sarcurr

Answer 1

No, <- is single assignment and tuple is immutable in F#.

You can define an infix function for the purpose (one-liner suggestion by @bytebuster):

let (>-<) x y = let temp = !x in x := !y; y := temp

// Usage
let a = ref [|1|]
let b = ref [|2|]
a >-< b