Theory Countable_Generator
section ‹Countable Datatypes›
theory Countable_Generator
imports
"HOL-Library.Countable"
"../Derive_Manager"
begin
text ‹
Brian Huffman and Alexander Krauss (old datatype), and Jasmin Blanchette (BNF datatype)
have developed tactics which automatically can prove that a datatype is countable.
We just make this tactic available in the derive-manager so that
one can conveniently write \texttt{derive countable some-datatype}.
›
subsection "Installing the tactic"
text ‹
There is nothing more to do, then to write some boiler-plate ML-code
for class-instantiation.
›
setup ‹
let
fun derive dtyp_name _ thy =
let
val base_name = Long_Name.base_name dtyp_name
val _ = writeln ("proving that datatype " ^ base_name ^ " is countable")
val sort = @{sort countable}
val vs =
let val i = BNF_LFP_Compat.the_spec thy dtyp_name |> #1
in map (fn (n,_) => (n, sort)) i end
val thy' = Class.instantiation ([dtyp_name],vs,sort) thy
|> Class.prove_instantiation_exit (fn ctxt => countable_tac ctxt 1)
val _ = writeln ("registered " ^ base_name ^ " in class countable")
in thy' end
in
Derive_Manager.register_derive "countable" "register datatypes is class countable" derive
end
›
end