From 1e10b27f69f1704b40dc36f87c1f276976cf1a72 Mon Sep 17 00:00:00 2001
From: Timothy Farrell <tim@thecookiejar.me>
Date: Thu, 2 Nov 2017 00:19:57 -0500
Subject: [PATCH] Rudimentary support for comparators.

---
 packages/frptools/src/computed.js   | 4 ++--
 packages/frptools/src/observable.js | 6 ++++--
 packages/frptools/src/util.js       | 1 +
 3 files changed, 7 insertions(+), 4 deletions(-)
 create mode 100644 packages/frptools/src/util.js

diff --git a/packages/frptools/src/computed.js b/packages/frptools/src/computed.js
index dbfff1d..a7009ea 100644
--- a/packages/frptools/src/computed.js
+++ b/packages/frptools/src/computed.js
@@ -1,4 +1,4 @@
-export function computed(fn, dependencies = []) {
+export function computed(fn, dependencies = [], comparator = eq) {
 	const subscribers = new Set();
 	const dependents = new Set();
 	let isDirty = true;
@@ -21,7 +21,7 @@ export function computed(fn, dependencies = []) {
 		if (isDirty) {
 			const newVal = fn.apply(null, dependencies.map(runParam));
 			isDirty = false;
-			if (newVal !== val) {
+			if (!comparator(newVal, val)) {
 				val = newVal;
 				subscribers.forEach(s => s(val));
 			}
diff --git a/packages/frptools/src/observable.js b/packages/frptools/src/observable.js
index 66d57ce..6c6180f 100644
--- a/packages/frptools/src/observable.js
+++ b/packages/frptools/src/observable.js
@@ -1,8 +1,10 @@
-export function observable(store) {
+import { eq } from './util.js';
+
+export function observable(store, comparator = eq) {
 	const subscribers = new Set();
 
 	const accessor = function _observable(newVal) {
-		if (newVal !== undefined && store !== newVal) {
+		if (newVal !== undefined && !comparator(store, newVal)) {
 			store = newVal;
 			subscribers.forEach(s => s(store));
 		}
diff --git a/packages/frptools/src/util.js b/packages/frptools/src/util.js
new file mode 100644
index 0000000..4ce0d59
--- /dev/null
+++ b/packages/frptools/src/util.js
@@ -0,0 +1 @@
+export const eq = (a, b) => a === b;