(* Title: Pure/General/alist.ML
ID: $Id$
Author: Florian Haftmann, TU Muenchen
Association lists -- lists of (key, value) pairs with unique keys.
A light-weight representation of finite mappings;
see also Pure/General/table.ML for a more scalable implementation.
*)
signature ALIST =
sig
exception DUP
val lookup: ('a * 'b -> bool) -> ('b * 'c) list -> 'a -> 'c option
val defined: ('a * 'b -> bool) -> ('b * 'c) list -> 'a -> bool
val update: ('a * 'a -> bool) -> ('a * 'b)
-> ('a * 'b) list -> ('a * 'b) list
val default: ('a * 'a -> bool) -> ('a * 'b)
-> ('a * 'b) list -> ('a * 'b) list
val delete: ('a * 'b -> bool) -> 'a
-> ('b * 'c) list -> ('b * 'c) list
val map_entry: ('a * 'b -> bool) -> 'a -> ('c -> 'c)
-> ('b * 'c) list -> ('b * 'c) list
val make: ('a -> 'b) -> 'a list -> ('a * 'b) list
val join: ('a * 'a -> bool) -> ('a -> 'b * 'b -> 'b option) ->
('a * 'b) list * ('a * 'b) list -> ('a * 'b) list (*exception DUP*)
val merge: ('a * 'a -> bool) -> ('b * 'b -> bool)
-> ('a * 'b) list * ('a * 'b) list -> ('a * 'b) list (*exception DUP*)
val find: ('a * 'b -> bool) -> ('c * 'b) list -> 'a -> 'c list
end;
structure AList: ALIST =
struct
fun find_index eq xs key =
let
fun find [] _ = 0
| find ((key', value)::xs) i =
if eq (key, key')
then i
else find xs (i+1);
in find xs 1 end;
fun lookup _ [] _ = NONE
| lookup eq ((key, value)::xs) key' =
if eq (key', key) then SOME value
else lookup eq xs key';
fun defined _ [] _ = false
| defined eq ((key, value)::xs) key' =
eq (key', key) orelse defined eq xs key';
fun update eq (x as (key, value)) xs =
let
val i = find_index eq xs key;
fun upd 1 (_::xs) = (x::xs)
| upd i (x::xs) = x :: upd (i-1) xs;
in if i = 0 then x::xs else upd i xs end;
fun default eq (key, value) xs =
if defined eq xs key then xs else (key, value)::xs;
fun delete eq key xs =
let
val i = find_index eq xs key;
fun del 1 (_::xs) = xs
| del i (x::xs) = x :: del (i-1) xs;
in if i = 0 then xs else del i xs end;
fun map_entry eq key f xs =
let
val i = find_index eq xs key;
fun mapp 1 ((x as (key, value))::xs) = (key, f value) :: xs
| mapp i (x::xs) = x :: mapp (i-1) xs;
in if i = 0 then xs else mapp i xs end;
exception DUP;
fun join eq f (xs, ys) =
let
fun add (key, x) xs =
(case lookup eq xs key of
NONE => update eq (key, x) xs
| SOME y =>
(case f key (y, x) of
SOME z => update eq (key, z) xs
| NONE => raise DUP));
in fold_rev add xs ys end;
fun merge eq_key eq_val (xs, ys) =
let
fun add (x as (key, value)) ys =
case lookup eq_key ys key
of NONE => update eq_key x ys
| SOME value' =>
if eq_val (value, value')
then ys
else raise DUP;
in fold_rev add xs ys end;
fun make keyfun =
let fun keypair x = (x, keyfun x)
in map keypair end;
fun find eq [] _ = []
| find eq ((key, value) :: xs) value' =
let
val values = find eq xs value';
in if eq (value', value) then key :: values else values end;
end;