anchor.diff:  
   /// Operations on first-class synchronous operations or alternatives.
   module Alt =
  +  //# Basic alternatives
  +
     /// Creates an alternative that is always available and results in the given
     /// value.
     ///
  
positive.code:   /// `choosy` is likely to be fastest.
  #endif
    val choosy: array<#Alt<'x>> -> Alt<'x>
  
    /// `chooser xAs` is like `choose xAs` except that the order in which the
    /// alternatives from the sequence are considered will be determined at random
    /// each time the alternative is used.  See also: `<~>`.
    val chooser:  seq<#Alt<'x>> -> Alt<'x>
  
    /// Creates an alternative whose result is passed to the given job constructor
    /// and processed with the resulting job after the given alternative has been
    /// committed to.  This is the same as `^=>` with the arguments flipped.
  
negative.code: #endif
    val inline once: 'x -> Alt<'x>
  
    //# Before actions
  
    /// Creates an alternative that is computed at instantiation time with the
    /// given job.  See also: `*<-=>-`, `prepareFun`, `withNackJob`.
  