Functional application: Allow any granularity of arguments (currying, essentially).

doc/API.md

@@ -295,9 +295,9 @@ channel.slice(10);
 Channel.slice(10, Infinity, channel);
 ```
 
-You can also use partial application to pass the channel in later:
+You can also use partial application:
 
 ```JavaScript
-const skipTen = Channel.slice(10, Infinity);
-skipTen(channel);
+Channel.slice(10, Infinity)(channel);
+Channel.slice(10)(Infinity)(channel);
 ```

lib/index.js

@@ -339,23 +339,22 @@ Channel.select = methodPromises =>
 // functional interface allowing full or partial application
 //
 // Channel.slice(10, Infinity, channel)
-//
-// or
-//
-// const skipTen = Channel.slice(10, Infinity)
-// skipTen(channel)
+// Channel.slice(10, Infinity)(channel)
+// Channel.slice(10)(Infinity)(channel)
 
 const channel = Channel();
 const methods = Object.keys(channel).concat(Object.keys(channel.readOnly()));
 
 methods.forEach(method => {
-  Channel[method] = (...args) => {
+  const bound = function(...args) {
     const arity = method === `slice` ? 3 : channel[method].length;
 
     return args.length >= arity
       ? args[arity - 1][method](...args.slice(0, arity - 1))
-      : channel => channel[method](...args);
+      : bound.bind(this, ...args);
   };
+
+  Channel[method] = bound;
 });
 
 module.exports = Object.freeze(Channel);

test/index.js

@@ -129,26 +129,6 @@ describe(`Channel`, function() {
 });
 
 describe(`functional interface`, async function() {
-  describe(`map`, function() {
-    it(`full application`, async function() {
-      assert.deepEqual(
-        await toArray(
-          Channel.map(value => value.toUpperCase(), Channel.of(`a`, `b`, `c`))
-        ),
-        [`A`, `B`, `C`]
-      );
-    });
-
-    it(`partial application`, async function() {
-      assert.deepEqual(
-        await toArray(
-          Channel.map(value => value.toUpperCase())(Channel.of(`a`, `b`, `c`))
-        ),
-        [`A`, `B`, `C`]
-      );
-    });
-  });
-
   describe(`slice`, function() {
     it(`full application`, async function() {
       assert.deepEqual(
@@ -157,7 +137,14 @@ describe(`functional interface`, async function() {
       );
     });
 
-    it(`partial application`, async function() {
+    it(`single argument application`, async function() {
+      assert.deepEqual(
+        await toArray(Channel.slice(1)(4)(Channel.of(0, 1, 2, 3, 4))),
+        [1, 2, 3]
+      );
+    });
+
+    it(`double argument application`, async function() {
       assert.deepEqual(
         await toArray(Channel.slice(1, 4)(Channel.of(0, 1, 2, 3, 4))),
         [1, 2, 3]