From 1fc2308f081fe4dbb65036502af9d6ed6c767b2e Mon Sep 17 00:00:00 2001
From: David Braun <David@NodeGuy.com>
Date: Tue, 28 Nov 2017 11:39:37 -0500
Subject: [PATCH] reduce: Require `initialValue` in functional interface.

---
 lib/index.js  | 7 ++++++-
 test/index.js | 2 ++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/index.js b/lib/index.js
index 88fddf7..a2618e5 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -407,9 +407,14 @@ const methods = Object.keys(channel).filter(
   method => typeof channel[method] === `function`
 );
 
+const arities = {
+  reduce: 2,
+  slice: 2
+};
+
 methods.forEach(method => {
   const bound = function(...args) {
-    const arity = method === `slice` ? 2 : channel[method].length;
+    const arity = arities[method] || channel[method].length;
 
     return args.length > arity
       ? args[arity][method](...args.slice(0, arity))
diff --git a/test/index.js b/test/index.js
index 8c1e7c5..87019c4 100644
--- a/test/index.js
+++ b/test/index.js
@@ -176,6 +176,8 @@ describe(`functional interface`, async function() {
     });
 
     it(`double argument application`, async function() {
+      assert.equal(await Channel.reduce(Math.max, 10, Channel.of(0, 1, 2)), 10);
+
       assert.deepEqual(
         await Channel.slice(1, 4)(Channel.of(0, 1, 2, 3, 4)).values(),
         [1, 2, 3]