(* Title: ZF/List
ID: $Id$
Author: Lawrence C Paulson, Cambridge University Computer Laboratory
Copyright 1994 University of Cambridge
Lists in Zermelo-Fraenkel Set Theory
map is a binding operator -- it applies to meta-level functions, not
object-level functions. This simplifies the final form of term_rec_conv,
although complicating its derivation.
*)
List = Datatype +
consts
"@" :: [i,i]=>i (infixr 60)
list_rec :: [i, i, [i,i,i]=>i] => i
map :: [i=>i, i] => i
length,rev :: i=>i
flat :: i=>i
list_add :: i=>i
hd,tl :: i=>i
drop :: [i,i]=>i
(* List Enumeration *)
"[]" :: i ("[]")
"@List" :: is => i ("[(_)]")
list :: i=>i
datatype
"list(A)" = Nil | Cons ("a:A", "l: list(A)")
translations
"[x, xs]" == "Cons(x, [xs])"
"[x]" == "Cons(x, [])"
"[]" == "Nil"
defs
hd_def "hd(l) == list_case(0, %x xs.x, l)"
tl_def "tl(l) == list_case(Nil, %x xs.xs, l)"
drop_def "drop(i,l) == rec(i, l, %j r. tl(r))"
list_rec_def
"list_rec(l,c,h) == Vrec(l, %l g.list_case(c, %x xs. h(x, xs, g`xs), l))"
map_def "map(f,l) == list_rec(l, Nil, %x xs r. Cons(f(x), r))"
length_def "length(l) == list_rec(l, 0, %x xs r. succ(r))"
app_def "xs@ys == list_rec(xs, ys, %x xs r. Cons(x,r))"
rev_def "rev(l) == list_rec(l, Nil, %x xs r. r @ [x])"
flat_def "flat(ls) == list_rec(ls, Nil, %l ls r. l @ r)"
list_add_def "list_add(l) == list_rec(l, 0, %x xs r. x#+r)"
end