link printf,ximage

procedure main()

   knot    := makeknot()     # create a structure with loops
   knota   := knot           # copy by assignment (reference)
   knotc   := copy(knot)     # built-in copy (shallow)
   knotdc  := deepcopy(knot) # deep copy


   showdeep("knota  (assignment) vs. knot",knota,knot)
   showdeep("knotc  (copy)  vs. knot",knotc,knot)
   showdeep("knotdc (deepcopy)  vs. knot",knotdc,knot)

   xdump("knot   (original)",knot)
   xdump("knota  (assignment)",knota)
   xdump("knotc  (copy)",knotc)
   xdump("knotdc (deepcopy)",knotdc)
end

record rec1(a,b,c)      # record for example

class Class1(a1,a2)     # class - looks like a record under the covers
   method one()
      self.a1 := 1
      return
   end
initially
   self.a1 := 0
end


procedure makeknot()    #: return a homogeneous structure with loops
   L := [9,8,7]
   T := table()
   T["a"] := 1
   R := rec1(T)
   S := set(R)
   C := Class1()
   C.one()
   T["knot"] := [L,R,S,C]
   put(L,R,S,T,C)
   return L
end

procedure showdeep(tag,XC,X)    #: demo to show (non-)equivalence of list elements
   printf("Analysis of copy depth for %s:\n",tag)
   showequiv(XC,X)
   every showequiv(XC[i := 1 to *X],X[i])
end

procedure showequiv(x,y)       #: show (non-)equivalence of two values
   return printf("   %i %s %i\n",x,if x === y then "===" else "~===",y)
end