AccessControl.fs

// Specification that the input parameter of the access-controlled function should satisfy
let spec = 
    Spec.def<string> 
    |> Spec.notEmpty "should not be empty string"
        
// The function (fun x -> Some x) is now 'access-controlled' with a specifiation for non-empty strings, 
// can be revoked anytime the 'Access.revoke acc' is called, and can only be accessed three times. 
let acc =
    Access.func (fun x -> Some x)
    |> Access.satisfy spec
    |> Access.revokable
    |> Access.times 3
    
// Revoke the function
Access.revoke acc
    
// Only files from within the '/bin' directory and file extension '.txt' are allowed to pass
let acc = access {
    onlyFilesFrom (DirectoryInfo "/bin")
    fileExtension ".txt" }

// Evalute 'access-controlled' function with file '/bin/image.jpg' 
let (result : Result<FileInfo, string list>) = Access.eval (FileInfo "/bin/image.jpg") acc