flatten:= proc(x)
options `Maple Advisor Database 1.00 for Maple V Release 4 and 5`,
`Copyright (c) 1998 by Robert B. Israel.  All rights reserved`;
   if type(x,set) then op(map(flatten,[op(x)]))
   elif type(x,list) then op(map(flatten,x))
   elif type(x,{table,array}) then 
     if nargs = 2 and args[2] = false then
       op(map(flatten,[entries(x)])) 
     else op(map(flatten@rhs,sort(op(-1,eval(x)),`flatten/comp`)))
     fi
   else x
   fi 
end;

`flatten/comp` := proc (s, t) 
options `Maple Advisor Database 1.00 for Maple V Release 4 and 5`,
`Copyright (c) 1998 by Robert B. Israel.  All rights reserved`;
local is, it, ns, nt, R; 
  is := op(1,s); 
  it := op(1,t); 
  ns := nops([is]); 
  nt := nops([it]); 
  if ns <> nt then RETURN(ns < nt) 
  elif ns > 1 then 
    if is[1] = it[1] then `flatten/comp`((is[2 .. ns])=0,(it[2 .. ns])=0) 
    else `flatten/comp`(is[1]=0,it[1]=0) 
    fi 
  elif type([is, it],list(realcons)) then evalb(is < it) 
  elif type([is, it],list(string)) then lexorder(is,it) 
  else R := [is, it]; evalb(R = sort(R)) 
  fi 
end;