map_css: explicitly provide a temporary context, which might be required for mksimps, mkcongs etc.;
(*  Title:      HOL/Modelcheck/MuCalculus.thy
    Author:     Olaf Mueller, Jan Philipps, Robert Sandner
    Copyright   1997  TU Muenchen
*)
theory MuCalculus
imports Main
begin
types
 'a pred = "'a=>bool"
definition Charfun :: "'a set => 'a pred" where
  "Charfun == (% A.% x. x:A)"
definition monoP  :: "('a pred => 'a pred) => bool" where
  "monoP f == mono(Collect o f o Charfun)"
definition mu :: "('a pred => 'a pred) => 'a pred" (binder "Mu " 10) where
  "mu f == Charfun(lfp(Collect o f o Charfun))"
definition nu :: "('a pred => 'a pred) => 'a pred" (binder "Nu " 10) where
  "nu f == Charfun(gfp(Collect o f o Charfun))"
end