diff options
Diffstat (limited to 'src/org/clojure/runtime/ListMap.java')
| -rw-r--r-- | src/org/clojure/runtime/ListMap.java | 34 |
1 files changed, 24 insertions, 10 deletions
diff --git a/src/org/clojure/runtime/ListMap.java b/src/org/clojure/runtime/ListMap.java index a87a699a..16c77e9c 100644 --- a/src/org/clojure/runtime/ListMap.java +++ b/src/org/clojure/runtime/ListMap.java @@ -14,6 +14,18 @@ package org.clojure.runtime; import java.util.Iterator; +/** + * Immplementation of persistent map on a linked list + + * Note that instances of this class are constant values + * i.e. add/remove etc return new values + * + * Lookups/changes are linear, so only appropriate for _very_small_ maps + * ArrayMap is generally faster, but this class avoids the double allocation, + * and so is better/faster as a bucket for hash tables + * + * null keys and values are ok, but you won't be able to distinguish a null value via get - use contains/find + */ public class ListMap implements IMap, IMapEntry { @@ -194,16 +206,14 @@ static class Link extends ListMap{ } public ListMap put(Object key, Object val){ - if(equalKey(key,_key)) + IMapEntry e = find(key); + if(e != null) { - if(val == _val) + if(e.val() == val) return this; - return new Link(key,val,_rest); + return create(_key,_val,remove(key)); } - ListMap r = _rest.put(key,val); - if(r == _rest) //already there with same value - return this; - return new Link(_key,_val,r); + return new Link(key,val,this); } public ListMap remove(Object key){ @@ -212,9 +222,7 @@ static class Link extends ListMap{ ListMap r = _rest.remove(key); if(r == _rest) //not there return this; - if(r == EMPTY) - return new Tail(_key,_val); - return new Link(_key, _val, r); + return create(_key,_val,r); } public Object get(Object key){ @@ -228,6 +236,12 @@ static class Link extends ListMap{ return count(); } + ListMap create(Object k,Object v,ListMap r){ + if(r == EMPTY) + return new Tail(k,v); + return new Link(k, v, r); + } + } boolean equalKey(Object k1,Object k2){ |