Add Future.bichain

index.js

@@ -15,6 +15,7 @@ export {ap} from './src/ap.js';
 export {attemptP} from './src/attempt-p.js';
 export {attempt} from './src/attempt.js';
 export {bimap} from './src/bimap.js';
+export {bichain} from './src/bichain.js';
 export {both} from './src/both.js';
 export {cache} from './src/cache.js';
 export {chainRej} from './src/chain-rej.js';

src/bichain.js

@@ -0,0 +1,18 @@
+import {createTransformation, future, application1, application, func} from './future.js';
+import {call} from './internal/utils.js';
+
+export var BichainTransformation = createTransformation(2, 'bichain', {
+  rejected: function BichainTransformation$rejected(x){ return call(this.$1, x) },
+  resolved: function BichainTransformation$resolved(x){ return call(this.$2, x) }
+});
+
+export function bichain(f){
+  var context1 = application1(bichain, func, arguments);
+  return function bichain(g){
+    var context2 = application(2, bichain, func, arguments, context1);
+    return function bichain(m){
+      var context3 = application(3, bichain, future, arguments, context1, context2);
+      return m._transform(new BichainTransformation(context3, f, g));
+    };
+  };
+}

test/prop/0.algebra.js

@@ -5,6 +5,7 @@ import {
   alt,
   and,
   ap,
+  bichain,
   bimap,
   cache,
   chain,
@@ -54,6 +55,14 @@ property('ap composition using map', _mx, _mf, _mf, function (mx, mf, mg){
   return eq(ap(mx)(ap(mf)(map(B)(mg))))(ap(ap(mx)(mf))(mg));
 });
 
+property('bichain left identity', _x, _fm, function (x, f){
+  return eq(bichain(f)(reject)(reject(x)))(f(x));
+});
+
+property('bichain right identity', _x, _fm, function (x, f){
+  return eq(bichain(resolve)(f)(resolve(x)))(f(x));
+});
+
 property('bimap identity', _mx, function (mx){
   return eq(bimap(I)(I)(mx))(mx);
 });

test/prop/2.arbitrary.js

@@ -13,6 +13,7 @@ import {
 import {
   after,
   and,
+  bichain,
   bimap,
   chain,
   chainRej,
@@ -90,6 +91,14 @@ property('mapRej(f)(m) = bimap(f)(I)(m)', anyFuture, function (m){
   return eq(mapRej(f)(m))(bimap(f)(I)(m));
 });
 
+property('Rejected m => chainRej(B(mk)(f))(m) = bichain(B(mk)(f))(reject)(m)', make, anyRejectedFuture, function (mk, m){
+  return eq(chainRej(B(mk)(f))(m))(bichain(B(mk)(f))(reject)(m));
+});
+
+property('Resolved m => chain(B(mk)(f))(m) = bichain(resolve)(B(mk)(f))(m)', make, anyResolvedFuture, function (mk, m){
+  return eq(chain(B(mk)(f))(m))(bichain(resolve)(B(mk)(f))(m));
+});
+
 property('mapRej(f)(m) = swap(map(f)(swap(m)))', anyFuture, function (m){
   return eq(mapRej(f)(m))(swap(map(f)(swap(m))));
 });

test/unit/4.bichain.js

@@ -0,0 +1,26 @@
+import {bichain} from '../../index.js';
+import {test, assertCrashed, assertRejected, assertResolved, assertValidFuture, eq, throwing, error} from '../util/util.js';
+import {testFunction, functionArg, futureArg} from '../util/props.js';
+import {resolvedSlow, resolved, rejected, rejectedSlow} from '../util/futures.js';
+import {resolve, reject} from '../../index.js';
+
+testFunction('bichain', bichain, [functionArg, functionArg, futureArg], assertValidFuture);
+
+test('runs a bichain transformation on Futures', function (){
+  return Promise.all([
+    assertResolved(bichain(reject)(resolve)(resolved), 'resolved'),
+    assertResolved(bichain(reject)(resolve)(resolvedSlow), 'resolvedSlow'),
+    assertRejected(bichain(resolve)(reject)(resolved), 'resolved'),
+    assertRejected(bichain(resolve)(reject)(resolvedSlow), 'resolvedSlow'),
+    assertResolved(bichain(resolve)(reject)(rejected), 'rejected'),
+    assertResolved(bichain(resolve)(reject)(rejectedSlow), 'rejectedSlow'),
+    assertRejected(bichain(reject)(resolve)(rejected), 'rejected'),
+    assertRejected(bichain(reject)(resolve)(rejectedSlow), 'rejectedSlow'),
+    assertCrashed(bichain(throwing)(reject)(rejected), error),
+    assertCrashed(bichain(resolve)(throwing)(resolved), error),
+  ]);
+});
+
+test('displays correctly as string', function (){
+  eq(bichain(resolve)(reject)(resolved).toString(), 'bichain (' + resolve.toString() + ') (' + reject.toString() + ') (resolve ("resolved"))');
+});