Question

I’m reading the book ‘Beginning F#’,
There’s a short list for example code, to demonstrate the lazy evaluation as follows:

lazyValue = lazy ( 2 + 2 )
let actualValue = Lazy.force lazyValue
printfn "%i" actualValue

It seems easy, but there’s a error to me, say that function force isn’t defined???

I’m confused about that. Searching from the msdn, it seems no answer.

Anyone can tell me what happened??

Answer 1

For some reason, Lazy.force is in F# PowerPack now.

Since this function doesn’t have dependency, I suggest you to copy it from F# PowerPack for convenient use:

module Lazy =
    let force (x: Lazy<'T>) = x.Force()