The mutable variable 'i' is used in an invalid way.?

f#

Solution

You can't refer to mutables inside a closure, and that includes such constructs as seq{} and async{} blocks.

You could write

let printProcess = async {
        let i = ref 1
        while true do
            System.Console.WriteLine(!i)
            i := !i + 1
    }

See this blog for some discussion.

Problem

I am attempting to write some simple code in F#, and i get this error: ``` Error 1 The mutable variable 'i' is used in an invalid way. Mutable variables may not be captured by closures. Consider eliminating this use of mutation or using a heap-allocated mutable reference cell via 'ref' and '!' ``` Code: ``` let printProcess = async { let mutable i = 1; while true do System.Console.WriteLine(i);//error is here i <- i + 1; } ``` Why won't it let me print the variable?

Original source