reorganize directory and file structure

lib/structures/dict.js

@@ -0,0 +1,22 @@
+import { RBTreeWrapper } from "../util/rbtree_wrapper.js";
+import { newProduct } from "./product.js";
+import { newLeft, newRight } from "./sum.js";
+
+export const emptyDict = compareFn => RBTreeWrapper.new((x, y) => compareFn(x)(y));
+
+export const has = dict => key => dict.tree.get(key) === true;
+export const set = dict => key => value => new RBTreeWrapper(dict.tree.remove(key).insert(key, value));
+export const remove = dict => key => new RBTreeWrapper(dict.tree.remove(key));
+export const length = dict => dict.tree.length;
+
+export const first = dict => dict.tree.begin;
+export const last  = dict => dict.tree.end;
+
+export const read = iter => {
+  if (iter !== undefined && iter.valid) {
+    return newRight(newProduct(newProduct(iter.key)(iter.value))(iter.clone().next()));
+  }
+  else {
+    return newLeft(unit);
+  }
+};