mg/src/TypeSelector.ig

 Copyright (C) 1992, Digital Equipment Corporation                         
 All rights reserved.                                                      
 See the file COPYRIGHT for a full description.                            
                                                                           
 by Steve Glassman and Mick Jordan                                         
 Last modified on Tue Jun  9 19:36:02 1992 by steveg   


| TypeSelector.ig and TypeSelector.mg generate a Selector proc
    (see MGV.i3) which iterates over all elements in the current
    MG VBT and finds the element that is a subtype of Type that
    is closest to the selection point.


    Likely Usage:
    

    file Piddly.i3:


    INTERFACE Piddly;
    IMPORT <Some interface with an interesting type>;
    TYPE Type = <interface>.<MG.T subtype>;
    END Piddly.


    file PiddlySelector.i3:


    INTERFACE PiddlySelector = TypeSelector()
    END PiddlySelector.


    file PiddlySelector.m3:


    MODULE PiddlySelector = TypeSelector(Piddly)
    END PiddlySelector.


    zeus view implementation:


    ...
    PROCEDURE Install(view: T) =
    VAR v := 
      NEW(<MGV.V subtype>, selector := PiddlySelector.closest, ...).init(...)
    BEGIN
      View.T.install(view);
      ...
    END Install;
    ...


    m3makefile:


    [Ii]nterface(Piddly)
    [Mm]odule(PiddlySelector)





GENERIC INTERFACE TypeSelector();

IMPORT MGV;

VAR
  closest: MGV.Selector;

END TypeSelector.