use heuristic to determine whether to keep or drop an existing "let" -- and drop all higher-order lets
header {* Main HOL *}
theory Main
imports Plain Record Predicate_Compile Smallcheck Nitpick
begin
text {*
Classical Higher-order Logic -- only ``Main'', excluding real and
complex numbers etc.
*}
text {* See further \cite{Nipkow-et-al:2002:tutorial} *}
end