From 7a4bf574a5a7907f2071aeea5db627b476195914 Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Wed, 28 Feb 2018 15:58:13 -0500
Subject: [PATCH 01/13] Add `ap` method and a simple test

---
 lib/index.js | 21 +++++++++++++++++++++
 test/test.js | 10 ++++++++++
 2 files changed, 31 insertions(+)

diff --git a/lib/index.js b/lib/index.js
index 0c3effe..3a34f19 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -2210,6 +2210,27 @@ addMethod('flatMap', function (f) {
     return this.map(f).sequence();
 });
 
+/**
+ * Creates a new Stream of values by applying each item in a Stream to each
+ * value in a Stream of functions
+ *
+ * @id ap
+ * @section Higher-order Streams
+ * @name Stream.ap(m)
+ * @param {Stream} m - incoming stream of values to apply to function(s) in stream
+ * @api public
+ *
+ * var readFile = _.wrapCallback(fs.readFile);
+ * filenames.flatMap(readFile)
+ */
+
+addMethod('ap', function (m) {
+    return this.map(function (f) {
+        return m.fork().map(f);
+    })
+      .parallel(Infinity);
+});
+
 /**
  * Retrieves values associated with a given property from all elements in
  * the collection.
diff --git a/test/test.js b/test/test.js
index d18ef6b..2afbc7b 100755
--- a/test/test.js
+++ b/test/test.js
@@ -4938,6 +4938,16 @@ exports['flatMap - map to Stream of Array'] = function (test) {
     });
 };
 
+exports.ap = function (test) {
+    function doubled(x) {
+        return x * 2;
+    }
+    _.ap(_([1, 2, 3, 4]), _.of(doubled)).toArray(function (xs) {
+        test.same(xs, [2, 4, 6, 8]);
+        test.done();
+    });
+};
+
 exports.pluck = function (test) {
     var a = _([
         {type: 'blogpost', title: 'foo'},

From 3aee195535c783d7b526eae56163491a13f2aad6 Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Mon, 22 Oct 2018 15:32:55 -0400
Subject: [PATCH 02/13] Add some tests per PR comments

---
 test/test.js | 97 +++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 89 insertions(+), 8 deletions(-)

diff --git a/test/test.js b/test/test.js
index 2afbc7b..6e875f9 100755
--- a/test/test.js
+++ b/test/test.js
@@ -4938,14 +4938,95 @@ exports['flatMap - map to Stream of Array'] = function (test) {
     });
 };
 
-exports.ap = function (test) {
-    function doubled(x) {
-        return x * 2;
-    }
-    _.ap(_([1, 2, 3, 4]), _.of(doubled)).toArray(function (xs) {
-        test.same(xs, [2, 4, 6, 8]);
-        test.done();
-    });
+exports.ap = {
+    'applies values to functions': function (test) {
+        var s = _([1, 2, 3, 4]);
+        var f = _.of(function doubled(x) {
+            return x * 2;
+        });
+
+        _.ap(f, s).toArray(function (xs) {
+            test.same(xs, [2, 4, 6, 8]);
+            test.done();
+        });
+    },
+    'noValueOnError': noValueOnErrorTest(_.ap(_.of(1))),
+    'ArrayStream': function (test) {
+        var f = _.of(function (x) {
+            return _(function (push, next) {
+                setTimeout(function () {
+                    push(null, x * 2);
+                    push(null, _.nil);
+                }, 10);
+            });
+        });
+        _([1, 2, 3, 4]).ap(f).merge().toArray(function (xs) {
+            test.same(xs, [2, 4, 6, 8]);
+            test.done();
+        });
+    },
+    'GeneratorStream': function (test) {
+        var f = _.of(function (x) {
+            return _(function (push, next) {
+                setTimeout(function () {
+                    push(null, x * 2);
+                    push(null, _.nil);
+                }, 10);
+            });
+        });
+        var s = _(function (push, next) {
+            push(null, 1);
+            push(null, 2);
+            setTimeout(function () {
+                push(null, 3);
+                push(null, 4);
+                push(null, _.nil);
+            }, 10);
+        });
+        s.ap(f).merge().toArray(function (xs) {
+            test.same(xs, [2, 4, 6, 8]);
+            test.done();
+        });
+    },
+    'map to Stream of Array': function (test) {
+        test.expect(1);
+        var f = _.of(function (x) {
+            return _([[x]]);
+        });
+        var s = _([1, 2, 3, 4]).ap(f).merge().toArray(function (xs) {
+            test.same(xs, [[1], [2], [3], [4]]);
+            test.done();
+        });
+    },
+    'reflect timing of value and function arrival': function (test) {
+        test.expect(1);
+        var f = _(function (push, next) {
+            setTimeout(function () {
+                push(null, function (x) { return 'g1(' + x + ')'; });
+            }, 20);
+            setTimeout(function () {
+                push(null, function (x) { return 'g2(' + x + ')'; });
+                push(null, _.nil);
+            }, 60);
+        });
+        var s = _(function (push, next) {
+            setTimeout(function () {
+                push(null, 1);
+            }, 10);
+            setTimeout(function () {
+                push(null, 2);
+            }, 50);
+            setTimeout(function () {
+                push(null, 3);
+                push(null, _.nil);
+            }, 70);
+        });
+
+        s.ap(f).toArray(function (xs) {
+            test.same(xs, ['g1(1)', 'g1(2)', 'g2(2)', 'g2(3)']);
+            test.done();
+        });
+    },
 };
 
 exports.pluck = function (test) {

From 20096e839940505746946f10a4e84f65ca8f0b80 Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Mon, 22 Oct 2018 15:33:19 -0400
Subject: [PATCH 03/13] Implement `ap` using `merge/scan1`

---
 lib/index.js | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/lib/index.js b/lib/index.js
index 3a34f19..87582fe 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -2217,18 +2217,37 @@ addMethod('flatMap', function (f) {
  * @id ap
  * @section Higher-order Streams
  * @name Stream.ap(m)
- * @param {Stream} m - incoming stream of values to apply to function(s) in stream
+ * @param {Stream} m - incoming stream of function(s) to apply to value(s) in stream
  * @api public
  *
+ * var filenames = _(['foo', 'bar', 'baz']);
  * var readFile = _.wrapCallback(fs.readFile);
- * filenames.flatMap(readFile)
+ * filenames.ap(_(readFile));
  */
 
-addMethod('ap', function (m) {
-    return this.map(function (f) {
-        return m.fork().map(f);
-    })
-      .parallel(Infinity);
+addMethod('ap', function(m) {
+    return _([
+        this.map(function (u1) {
+            return {
+                u: u1
+            };
+        }),
+        m.map(function (m1) {
+            return {
+                m: m1
+            };
+        }),
+    ])
+        .merge()
+        .scan1(function (x, y) {
+            return Object.assign({}, x, y);
+        })
+        .filter(function (x) {
+            return x.u && x.m;
+        })
+        .map(function (x) {
+            return x.m(x.u);
+        });
 });
 
 /**

From 223467d91602a2fe45e620180a980e4bf377db14 Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Wed, 24 Oct 2018 11:52:03 -0400
Subject: [PATCH 04/13] Update `ap` example to use modulating `fns` values

---
 lib/index.js | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/lib/index.js b/lib/index.js
index 87582fe..378ac4f 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -2220,9 +2220,16 @@ addMethod('flatMap', function (f) {
  * @param {Stream} m - incoming stream of function(s) to apply to value(s) in stream
  * @api public
  *
- * var filenames = _(['foo', 'bar', 'baz']);
- * var readFile = _.wrapCallback(fs.readFile);
- * filenames.ap(_(readFile));
+ * var asyncUnit = () => h.of(h.nil);
+ * var asyncAutocomplete = e => h(fetch(`/autocomplete?s=${e.target.value}`));
+ *
+ * var fns = h('change', checkbox)
+ *   .flatMap(e => h.of(e.target.checked ? asyncAutocomplete : asyncUnit));
+ *
+ * h('change', input)
+ *   .ap(fns)
+ *   .merge()
+ *   .map(showAutocompleteResults);
  */
 
 addMethod('ap', function(m) {

From 0fe6feccecbb9cb047c466304ada0231fdcdb56d Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Wed, 24 Oct 2018 12:13:17 -0400
Subject: [PATCH 05/13] Test timing of arrival of functions and values with
 `ap`

---
 test/test.js | 44 ++++++++++++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 14 deletions(-)

diff --git a/test/test.js b/test/test.js
index 6e875f9..38fc726 100755
--- a/test/test.js
+++ b/test/test.js
@@ -4939,6 +4939,14 @@ exports['flatMap - map to Stream of Array'] = function (test) {
 };
 
 exports.ap = {
+    setUp: function (callback) {
+        this.clock = sinon.useFakeTimers();
+        callback();
+    },
+    tearDown: function (callback) {
+        this.clock.restore();
+        callback();
+    },
     'applies values to functions': function (test) {
         var s = _([1, 2, 3, 4]);
         var f = _.of(function doubled(x) {
@@ -4952,6 +4960,7 @@ exports.ap = {
     },
     'noValueOnError': noValueOnErrorTest(_.ap(_.of(1))),
     'ArrayStream': function (test) {
+        test.expect(1);
         var f = _.of(function (x) {
             return _(function (push, next) {
                 setTimeout(function () {
@@ -4962,26 +4971,24 @@ exports.ap = {
         });
         _([1, 2, 3, 4]).ap(f).merge().toArray(function (xs) {
             test.same(xs, [2, 4, 6, 8]);
-            test.done();
         });
+        this.clock.tick(20);
+        test.done();
     },
     'GeneratorStream': function (test) {
+        test.expect(1);
         var f = _.of(function (x) {
             return _(function (push, next) {
-                setTimeout(function () {
-                    push(null, x * 2);
-                    push(null, _.nil);
-                }, 10);
+                push(null, x * 2);
+                push(null, _.nil);
             });
         });
         var s = _(function (push, next) {
             push(null, 1);
             push(null, 2);
-            setTimeout(function () {
-                push(null, 3);
-                push(null, 4);
-                push(null, _.nil);
-            }, 10);
+            push(null, 3);
+            push(null, 4);
+            push(null, _.nil);
         });
         s.ap(f).merge().toArray(function (xs) {
             test.same(xs, [2, 4, 6, 8]);
@@ -4999,7 +5006,7 @@ exports.ap = {
         });
     },
     'reflect timing of value and function arrival': function (test) {
-        test.expect(1);
+        test.expect(4);
         var f = _(function (push, next) {
             setTimeout(function () {
                 push(null, function (x) { return 'g1(' + x + ')'; });
@@ -5022,10 +5029,19 @@ exports.ap = {
             }, 70);
         });
 
-        s.ap(f).toArray(function (xs) {
-            test.same(xs, ['g1(1)', 'g1(2)', 'g2(2)', 'g2(3)']);
-            test.done();
+        var results = [];
+        s.ap(f).each(function (x) {
+            results.push(x);
         });
+        this.clock.tick(20);
+        test.same(results, ['g1(1)']);
+        this.clock.tick(30);
+        test.same(results, ['g1(1)', 'g1(2)']);
+        this.clock.tick(10);
+        test.same(results, ['g1(1)', 'g1(2)', 'g2(2)']);
+        this.clock.tick(10);
+        test.same(results, ['g1(1)', 'g1(2)', 'g2(2)', 'g2(3)']);
+        test.done();
     },
 };
 

From 98f1b7da38a7815701c9ea299b91b9c6014fb9ae Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Wed, 24 Oct 2018 12:25:20 -0400
Subject: [PATCH 06/13] Test `composition` requirement of `ap`

per https://github.com/fantasyland/fantasy-land/blob/1871bd3f95ca47cf016f670c140c413a040c6869/README.md#apply
---
 test/test.js | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/test/test.js b/test/test.js
index 38fc726..6b03320 100755
--- a/test/test.js
+++ b/test/test.js
@@ -5043,6 +5043,43 @@ exports.ap = {
         test.same(results, ['g1(1)', 'g1(2)', 'g2(2)', 'g2(3)']);
         test.done();
     },
+    // v.ap(u.ap(a.map(f => g => x => f(g(x))))) is equivalent to v.ap(u).ap(a) (composition)
+    'composition': {
+        'left': function (test) {
+            test.expect(1);
+            var v = _.of('a');
+            var u = _.of(function (x) {
+                return x + 'b';
+            });
+            var a = _.of(function (x) {
+                return x + 'c';
+            });
+            v.fork().ap(u.fork().ap(a.fork().map(function (f) {
+                return function (g) {
+                    return function (x) {
+                        return f(g(x));
+                    };
+                };
+            }))).toArray(function (x) {
+                test.same(x, ['abc']);
+            });
+            test.done();
+        },
+        'right': function (test) {
+            test.expect(1);
+            var v = _.of('a');
+            var u = _.of(function (x) {
+                return x + 'b';
+            });
+            var a = _.of(function (x) {
+                return x + 'c';
+            });
+            v.ap(u).ap(a).toArray(function (x) {
+                test.same(x, ['abc']);
+            });
+            test.done();
+        },
+    },
 };
 
 exports.pluck = function (test) {

From a301ba81a8e1d36d0fac86555cdc14d2b0b4d71e Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Wed, 24 Oct 2018 12:39:47 -0400
Subject: [PATCH 07/13] Use `_.extend` instead of `Object.assign` in `ap`

This was breaking a build on an older Node version.

https://travis-ci.org/caolan/highland/jobs/445755627
---
 lib/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/index.js b/lib/index.js
index 86fa125..c3577b0 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -2274,7 +2274,7 @@ addMethod('ap', function(m) {
     ])
         .merge()
         .scan1(function (x, y) {
-            return Object.assign({}, x, y);
+            return _.extend(x, y);
         })
         .filter(function (x) {
             return x.u && x.m;

From 196b61f45c2607c13f1c50b3de851009c1cfb5c1 Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Wed, 24 Oct 2018 12:43:23 -0400
Subject: [PATCH 08/13] Correct argument order for `extend` in `ap`

duh
---
 lib/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/index.js b/lib/index.js
index c3577b0..69c2839 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -2274,7 +2274,7 @@ addMethod('ap', function(m) {
     ])
         .merge()
         .scan1(function (x, y) {
-            return _.extend(x, y);
+            return _.extend(y, x);
         })
         .filter(function (x) {
             return x.u && x.m;

From 00f330cdd1d5944234521469731710d47b1026be Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Thu, 25 Oct 2018 09:20:47 -0400
Subject: [PATCH 09/13] Use `_` instead of `h`

---
 lib/index.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/index.js b/lib/index.js
index 69c2839..2648c60 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -2247,13 +2247,13 @@ addMethod('flatMap', function (f) {
  * @param {Stream} m - incoming stream of function(s) to apply to value(s) in stream
  * @api public
  *
- * var asyncUnit = () => h.of(h.nil);
- * var asyncAutocomplete = e => h(fetch(`/autocomplete?s=${e.target.value}`));
+ * var asyncUnit = () => _.of(_.nil);
+ * var asyncAutocomplete = e => _(fetch(`/autocomplete?s=${e.target.value}`));
  *
- * var fns = h('change', checkbox)
+ * var fns = _('change', checkbox)
  *   .flatMap(e => h.of(e.target.checked ? asyncAutocomplete : asyncUnit));
  *
- * h('change', input)
+ * _('change', input)
  *   .ap(fns)
  *   .merge()
  *   .map(showAutocompleteResults);

From fd2c069dadf9dd50623ee9271ab26fdb0f2f5a59 Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Thu, 25 Oct 2018 09:21:54 -0400
Subject: [PATCH 10/13] `sequence` instead of `merge` in `ap` example for
 guaranteed order

---
 lib/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/index.js b/lib/index.js
index 2648c60..ac891ba 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -2255,7 +2255,7 @@ addMethod('flatMap', function (f) {
  *
  * _('change', input)
  *   .ap(fns)
- *   .merge()
+ *   .sequence()
  *   .map(showAutocompleteResults);
  */
 

From 0bdafe2e9faa0ee2744c6c03cd647f1866d4b0ea Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Thu, 25 Oct 2018 09:23:59 -0400
Subject: [PATCH 11/13] Correct `asyncUnit` empty stream in `ap` example

---
 lib/index.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/index.js b/lib/index.js
index ac891ba..db95a77 100755
--- a/lib/index.js
+++ b/lib/index.js
@@ -2247,11 +2247,11 @@ addMethod('flatMap', function (f) {
  * @param {Stream} m - incoming stream of function(s) to apply to value(s) in stream
  * @api public
  *
- * var asyncUnit = () => _.of(_.nil);
+ * var asyncUnit = () => _([]);
  * var asyncAutocomplete = e => _(fetch(`/autocomplete?s=${e.target.value}`));
  *
  * var fns = _('change', checkbox)
- *   .flatMap(e => h.of(e.target.checked ? asyncAutocomplete : asyncUnit));
+ *   .flatMap(e => _.of(e.target.checked ? asyncAutocomplete : asyncUnit));
  *
  * _('change', input)
  *   .ap(fns)

From 0d14e7f588930a5fc3d77a5809f1297ac4caf244 Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Thu, 25 Oct 2018 10:00:18 -0400
Subject: [PATCH 12/13] Consolidate `ap - composition` left/right tests

---
 test/test.js | 41 +++++++++++++++++------------------------
 1 file changed, 17 insertions(+), 24 deletions(-)

diff --git a/test/test.js b/test/test.js
index 1a493ce..170ef51 100755
--- a/test/test.js
+++ b/test/test.js
@@ -5102,40 +5102,33 @@ exports.ap = {
         test.same(results, ['g1(1)', 'g1(2)', 'g2(2)', 'g2(3)']);
         test.done();
     },
-    // v.ap(u.ap(a.map(f => g => x => f(g(x))))) is equivalent to v.ap(u).ap(a) (composition)
     'composition': {
-        'left': function (test) {
-            test.expect(1);
-            var v = _.of('a');
+        'v.ap(u.ap(a.map(f => g => x => f(g(x))))) is equivalent to v.ap(u).ap(a)': function (test) {
+            test.expect(3);
+            var v = _([1, 2, 3]);
             var u = _.of(function (x) {
-                return x + 'b';
+                return 'u(' + x + ')';
             });
             var a = _.of(function (x) {
-                return x + 'c';
+                return 'a(' + x + ')';
             });
-            v.fork().ap(u.fork().ap(a.fork().map(function (f) {
+            var left = v.fork().ap(u.fork().ap(a.fork().map(function (f) {
                 return function (g) {
                     return function (x) {
                         return f(g(x));
                     };
                 };
-            }))).toArray(function (x) {
-                test.same(x, ['abc']);
-            });
-            test.done();
-        },
-        'right': function (test) {
-            test.expect(1);
-            var v = _.of('a');
-            var u = _.of(function (x) {
-                return x + 'b';
-            });
-            var a = _.of(function (x) {
-                return x + 'c';
-            });
-            v.ap(u).ap(a).toArray(function (x) {
-                test.same(x, ['abc']);
-            });
+            })));
+            var right = v.observe().ap(u.observe()).ap(a.observe());
+
+            _([left.collect(), right.collect()])
+                .sequence()
+                .apply(function (lefts, rights) {
+                    test.same(lefts, ['a(u(1))', 'a(u(2))', 'a(u(3))']);
+                    test.same(rights, ['a(u(1))', 'a(u(2))', 'a(u(3))']);
+                    test.same(lefts, rights);
+                });
+
             test.done();
         },
     },

From cfb68d31b142bd2a78b45219cc9025a8987d7198 Mon Sep 17 00:00:00 2001
From: Matt Ross <amsross@gmail.com>
Date: Thu, 25 Oct 2018 10:09:16 -0400
Subject: [PATCH 13/13] Update CHANGELOG

---
 CHANGELOG.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 98e715f..653ae87 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,13 @@ This file does not aim to be comprehensive (you have git history for that),
 rather it lists changes that might impact your own code as a consumer of
 this library.
 
+3.0.0-beta.7
+-----
+
+### New additions
+* `ap` - Applies a stream of function(s) to the stream of value(s).
+  [#643](https://github.com/caolan/highland/pull/643).
+
 3.0.0-beta.6
 -----
 This release contains all changes from [2.12.0](#2120).