anchor.diff:    ///> let ( *<+=>- ) qCh rI2q = qCh *<+=>= (rI2q >> result)
   #endif
     val inline ( *<+=>- ): Ch<'q> -> (IVar<'r>                  ->      'q)  -> Alt<'r>
  -  
  +
  +  //# Message passing
  +
     /// Creates an alternative that, at instantiation time, offers to give the
     /// given value on the given channel, and becomes available when another job
     /// offers to take the value.  `xCh *<- x` is equivalent to `Ch.give xCh x`.
  
positive.code:   /// A memoizing version of `>>-!`.
    val inline ( >>-*! ): Job<_>  ->             exn  -> Promise<_>
  
    // Kleisli -------------------------------------------------------------------
  
    /// Creates a job that is the composition of the given two job constructors.
    /// `(x2yJ >=> y2zJ) x` is equivalent to `x2yJ x >>= y2zJ` and is much like
  
negative.code:   /// `xA ^->! e` is equivalent to `xA ^-> fun _ -> raise e`.
    val ( ^->! ): Alt<_>  ->             exn  -> Alt<_>
  
    //# Choices
  
    /// Creates an alternative that is available when either of the given
    /// alternatives is available.  `xA1 <|> xA2` is an optimized version of
  