!!! I was making an attempt to create a PAIR class, holding two possibly
!!! different items. Poking through the ISE libraries, I came upon
!!! CELL[G]. That seemed an appropriate class to use as a base for
!!! PAIR. So, here's the class that I came up with:
!!! 
!!! indexing
!!!    description: "Container for holding pairs of possibly non-related items."
!!!    status: "Mark Bolstad, bolstad@vislab.epa.gov, US EPA/LM"
!!!    names: pair, tuple
!!!    representation: cell
!!!    access: fixed
!!!    size: fixed
!!!    contents: generic
!!!    date: "$Date: 2001/11/16 20:33:19 $"
!!!    revision: "$Revision: 1.1.1.1 $"
!!! 
!!! class
!!! 
!!!    PAIR [G, H]
!!! 
!!! inherit
!!! 
!!!    CELL [G]
!!!       rename
!!!          item as left,
!!!          put as put_left,
!!!          replace as replace_left
!!!       select
!!!          left, put_left, replace_left
!!!       end
!!! 
!!!    CELL [H]
!!!       rename
!!!          item as right,
!!!          put as put_right,
!!!          replace as replace_right
!!!       end
!!! 
!!! creation
!!! 
!!!    put
!!! 
!!! feature -- Element change
!!! 
!!!    put, replace (v1: G; v2: H) is
!!!          -- Make `v1' the `left' and `v2' the `right'
!!!       do
!!!          put_left (v1)
!!!          put_right (v2)
!!!       ensure
!!!          left_inserted:  left  = v1
!!!          right_inserted: right = v2
!!!       end
!!! 
!!! end -- PAIR
!!! 
!!! [ISE] Eiffel complains with the following error:
!!! 
!!! ------------------------------------------
!!! Error code: VUAR(2)
!!! Type error: non-conforming actual argument in feature call.
!!! What to do: make sure that type of actual argument conforms to type
!!!   of corresponding formal argument.
!!! 
!!! Class: PAIR [G, H]
!!! Feature: put
!!! Called feature: put_right (v: [like feature]: Generic #1) from CELL
!!! Argument name: v
!!! Argument position: 1
!!! Actual argument type: Generic #2
!!! Formal argument type: Generic #1
!!! ------------------------------------------
!!! 
!!! The problem is the CELL[H]. I thought that the declaration would
!!! rename the parameter in the class. I could easily collapse the
!!! inheritance structure, but I want to know what is the solution to the
!!! problem as stated?
!!! 
!!! --
!!! --
!!!    Mark Bolstad
!!!    Visualization Specialist
!!!    Lockheed-Martin Technical Services
!!!    bolstad@vislab.epa.gov
!!!    (919)-541-3604