# HG changeset patch
# User haftmann
# Date 1128530308 -7200
# Node ID 10319da54a47af48f27c21c012d50a6667e371d4
# Parent  e3cd31bc2e409b820ddbd2390169c5abc7708978
added merge, tuned

diff -r e3cd31bc2e40 -r 10319da54a47 src/Pure/General/alist.ML
--- a/src/Pure/General/alist.ML	Wed Oct 05 14:01:32 2005 +0200
+++ b/src/Pure/General/alist.ML	Wed Oct 05 18:38:28 2005 +0200
@@ -9,6 +9,7 @@
 
 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)
@@ -20,12 +21,23 @@
   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 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
@@ -35,30 +47,44 @@
   | defined eq ((key, value)::xs) key' =
       eq (key', key) orelse defined eq xs key';
 
-fun update eq (key, value) xs =
+fun update eq (x as (key, value)) xs =
   let
-    fun upd ((x as (key', _))::xs) =
-      if eq (key, key')
-      then (key, value)::xs
-      else x :: upd xs
-  in if defined eq xs key then upd xs else (key, value)::xs end;
+    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
-    fun del ((x as (key', _))::xs) =
-      if eq (key, key') then xs
-      else x :: del xs;
-  in if defined eq xs key then del xs else xs end;
+    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;
 
-fun map_entry eq key' f xs =
+exception DUP;
+
+fun merge eq_key eq_val (xs, ys) =
   let
-    fun mapp ((x as (key, value))::xs) =
-      if eq (key', key) then (key, f value)::xs
-      else x :: mapp xs
-  in if defined eq xs key' then mapp xs else xs end;
+    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)
@@ -67,7 +93,7 @@
 fun find eq [] _ = []
   | find eq ((key, value) :: xs) value' =
       let
-        val values = find eq xs value'
+        val values = find eq xs value';
       in if eq (value', value) then key :: values else values end;
 
 end;