From 10c753b66fc124045c25a6aca208315e9fd2813d Mon Sep 17 00:00:00 2001
From: Oleksandr Avoiants <shhavel@gmail.com>
Date: Fri, 15 Nov 2019 00:14:20 +0200
Subject: [PATCH 1/4] Possible Exercises

---
 Exercises/2-closure.js    | 25 +++++++++++++++++++++++
 Exercises/2-closure.test  | 16 +++++++++++++++
 Exercises/3-lambda.js     | 11 ++++++++++
 Exercises/3-lambda.test   | 21 ++++++++++++++++++++
 Exercises/4-bind.js       | 35 ++++++++++++++++++++++++++++++++
 Exercises/4-bind.test     | 16 +++++++++++++++
 Exercises/5-curry.js      | 24 ++++++++++++++++++++++
 Exercises/5-curry.test    | 42 +++++++++++++++++++++++++++++++++++++++
 Exercises/6-chaining.js   | 15 ++++++++++++++
 Exercises/6-chaining.test | 18 +++++++++++++++++
 10 files changed, 223 insertions(+)
 create mode 100644 Exercises/2-closure.js
 create mode 100644 Exercises/2-closure.test
 create mode 100644 Exercises/3-lambda.js
 create mode 100644 Exercises/3-lambda.test
 create mode 100644 Exercises/4-bind.js
 create mode 100644 Exercises/4-bind.test
 create mode 100644 Exercises/5-curry.js
 create mode 100644 Exercises/5-curry.test
 create mode 100644 Exercises/6-chaining.js
 create mode 100644 Exercises/6-chaining.test

diff --git a/Exercises/2-closure.js b/Exercises/2-closure.js
new file mode 100644
index 0000000..3f9aab2
--- /dev/null
+++ b/Exercises/2-closure.js
@@ -0,0 +1,25 @@
+'use strict';
+
+const coffee = (volume, strength) =>
+  (`Coffee volume: ${volume}ml, strength: ${strength}`);
+
+const defineCoffeeType = volume => strength => coffee(volume, strength);
+
+// Use function defineCoffeeType to define new coffee types.
+// Define coffee type espresso which volume should equal 50ml.
+// Define coffee type americano which volume should equal 150ml.
+
+const espresso = null;
+const americano = null;
+
+// Set names for anonymous functions (for tests).
+if (typeof espresso === 'function') {
+  Object.defineProperty(espresso, 'name',
+    { value: 'espresso', configurable: true });
+}
+if (typeof americano === 'function') {
+  Object.defineProperty(americano, 'name',
+    { value: 'americano', configurable: true });
+}
+
+module.exports = { espresso, americano };
diff --git a/Exercises/2-closure.test b/Exercises/2-closure.test
new file mode 100644
index 0000000..f11cc0f
--- /dev/null
+++ b/Exercises/2-closure.test
@@ -0,0 +1,16 @@
+([{
+  name: 'espresso',
+  length: [30, 70],
+  cases: [
+    ['medium', 'Coffee volume: 50ml, strength: medium'],
+    ['strong', 'Coffee volume: 50ml, strength: strong'],
+  ]
+},
+{
+  name: 'americano',
+  length: [30, 70],
+  cases: [
+    ['medium', 'Coffee volume: 150ml, strength: medium'],
+    ['strong', 'Coffee volume: 150ml, strength: strong'],
+  ]
+}])
diff --git a/Exercises/3-lambda.js b/Exercises/3-lambda.js
new file mode 100644
index 0000000..994caa8
--- /dev/null
+++ b/Exercises/3-lambda.js
@@ -0,0 +1,11 @@
+'use strict';
+
+const tagged = (pref, str) => `[${pref}] ${str}`;
+
+// Define function tagDate that prepends current date to the string.
+// E.g. tagDate('My String') === '[2019-11-14] My String'
+// Use function tagged to implement tagDate.
+
+const tagDate = null;
+
+module.exports = { tagDate };
diff --git a/Exercises/3-lambda.test b/Exercises/3-lambda.test
new file mode 100644
index 0000000..d8dbc6e
--- /dev/null
+++ b/Exercises/3-lambda.test
@@ -0,0 +1,21 @@
+({
+  name: 'tagDate',
+  length: [150, 400],
+  test: tagDate => {
+    {
+      const today = new Date();
+      const dd = String(today.getDate()).padStart(2, '0');
+      const mm = String(today.getMonth() + 1).padStart(2, '0');
+      const yyyy = today.getFullYear();
+      const expected = `[${yyyy}-${mm}-${dd}] Test`;
+      const y = tagDate('Test');
+      if (y !== expected) {
+        throw new Error(`tagDate('Test') === ${y} expected: ${expected}`);
+      }
+    }
+    {
+      const src = tagDate.toString();
+      if (!src.includes('tagged(')) throw new Error('Use function tagged to implement tagDate');
+    }
+  }
+})
diff --git a/Exercises/4-bind.js b/Exercises/4-bind.js
new file mode 100644
index 0000000..4d869ba
--- /dev/null
+++ b/Exercises/4-bind.js
@@ -0,0 +1,35 @@
+'use strict';
+
+/*
+  Generalized mean (Hölder mean)
+  Given n numbers a₁, a₂, ... an
+  Define Hk (for k != 0) as the k-th root of the arithmetic mean
+  of the k-th power of a set of numbers
+         ____________________________
+  Hk = ᵏ√ (a₁ᵏ + a₂ᵏ + ... + anᵏ) / n
+*/
+
+const H = (exp, ...args) => {
+  const sum = args.reduce((s, a) => (s + Math.pow(a, exp)), 0);
+  const avg = sum / args.length;
+  return Math.pow(avg, (1 / exp));
+};
+
+// Use method bind() to create new functions from function H.
+// Create function `average` that returns arithmetic mean (H₁) of the arguments.
+// Create function `rootMeanSquare` that returns quadratic mean (H₂).
+
+const average = null;
+const rootMeanSquare = null;
+
+// Set names for anonymous functions (for tests).
+if (typeof average === 'function') {
+  Object.defineProperty(average, 'name',
+    { value: 'average', configurable: true });
+}
+if (typeof rootMeanSquare === 'function') {
+  Object.defineProperty(rootMeanSquare, 'name',
+    { value: 'rootMeanSquare', configurable: true });
+}
+
+module.exports = { average, rootMeanSquare };
diff --git a/Exercises/4-bind.test b/Exercises/4-bind.test
new file mode 100644
index 0000000..c280276
--- /dev/null
+++ b/Exercises/4-bind.test
@@ -0,0 +1,16 @@
+([{
+  name: 'rootMeanSquare',
+  length: [10, 70],
+  cases: [
+    [7, 1, 5],
+    [4, 4, 4, 4],
+  ]
+},
+{
+  name: 'average',
+  length: [10, 70],
+  cases: [
+    [3, 4, 6, 7, 5],
+    [4, 4, 4, 4],
+  ]
+}])
diff --git a/Exercises/5-curry.js b/Exercises/5-curry.js
new file mode 100644
index 0000000..7413db2
--- /dev/null
+++ b/Exercises/5-curry.js
@@ -0,0 +1,24 @@
+'use strict';
+
+// Check 4 digit pin.
+const checkPin = (ch1, ch2, ch3, ch4) =>
+  ([ch1, ch2, ch3, ch4].join('') === '4967');
+
+const curry = fn => (...args) =>
+  (fn.length > args.length ?
+    (...args2) =>
+      curry(fn)(...args, ...args2) :
+    fn(...args));
+
+// Use function curry to define function press
+// that allows to enter pin code by one character,
+// e.g. press('3')('4')('5')('6')
+
+const press = null;
+
+// Set name for anonymous function (for tests).
+if (typeof press === 'function') {
+  Object.defineProperty(press, 'name', { value: 'press', configurable: true });
+}
+
+module.exports = { press };
diff --git a/Exercises/5-curry.test b/Exercises/5-curry.test
new file mode 100644
index 0000000..6612626
--- /dev/null
+++ b/Exercises/5-curry.test
@@ -0,0 +1,42 @@
+({
+  name: 'press',
+  length: [50, 200],
+  test: press => {
+    {
+      const f1 = press('1');
+      if (typeof f1 !== 'function') {
+        throw new Error(`Expected press('1') to be a function.`);
+      }
+    }
+    {
+      const f2 = press('1')('2');
+      if (typeof f2 !== 'function') {
+        throw new Error(`Expected press('1')('2') to be a function.`);
+      }
+    }
+    {
+      const f3 = press('1')('2')('3');
+      if (typeof f3 !== 'function') {
+        throw new Error(`Expected press('1')('2')('3') to be a function.`);
+      }
+    }
+    {
+      const e4 = press('1')('2')('3')('4');
+      if (typeof e4 !== 'boolean') {
+        throw new Error(`Expected press('1')('2')('3')('4') to be a boolean.`);
+      }
+    }
+    {
+      const res = press('1')('2')('3')('4');
+      if (res) {
+        throw new Error(`Expected false when entered wrong pin code.`);
+      }
+    }
+    {
+      const res = press('4')('9')('6')('7');
+      if (!res) {
+        throw new Error(`Expected true when entered correct pin code.`);
+      }
+    }
+  }
+})
diff --git a/Exercises/6-chaining.js b/Exercises/6-chaining.js
new file mode 100644
index 0000000..9467775
--- /dev/null
+++ b/Exercises/6-chaining.js
@@ -0,0 +1,15 @@
+'use strict';
+
+// Check 4 digit pin.
+const checkPin = (ch1, ch2, ch3, ch4) =>
+  ([ch1, ch2, ch3, ch4].join('') === '4967');
+
+// Impement function press
+// that allows to enter pin code by one character,
+// e.g. press('3').press('4').press('5').press('6')
+//
+// For hint use https://github.com/HowProgrammingWorks/Cheatsheet
+
+const press = null;
+
+module.exports = { press };
diff --git a/Exercises/6-chaining.test b/Exercises/6-chaining.test
new file mode 100644
index 0000000..01d82a8
--- /dev/null
+++ b/Exercises/6-chaining.test
@@ -0,0 +1,18 @@
+({
+  name: 'press',
+  length: [50, 200],
+  test: press => {
+    {
+      const res = press('1').press('2').press('3').press('4');
+      if (res) {
+        throw new Error(`Expected false when entered wrong pin code.`);
+      }
+    }
+    {
+      const res = press('4').press('9').press('6').press('7');
+      if (!res) {
+        throw new Error(`Expected true when entered correct pin code.`);
+      }
+    }
+  }
+})

From c0d310e2f1ca2fb978d5ebb0a92dd88207cc678a Mon Sep 17 00:00:00 2001
From: Oleksandr Avoiants <shhavel@gmail.com>
Date: Fri, 15 Nov 2019 09:28:03 +0200
Subject: [PATCH 2/4] Change curry exercise

---
 Exercises/5-curry.js | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/Exercises/5-curry.js b/Exercises/5-curry.js
index 7413db2..48104f7 100644
--- a/Exercises/5-curry.js
+++ b/Exercises/5-curry.js
@@ -1,20 +1,17 @@
 'use strict';
 
 // Check 4 digit pin.
-const checkPin = (ch1, ch2, ch3, ch4) =>
-  ([ch1, ch2, ch3, ch4].join('') === '4967');
+const checkPin = (...code) =>
+  (code.join('') === '4967');
 
-const curry = fn => (...args) =>
-  (fn.length > args.length ?
-    (...args2) =>
-      curry(fn)(...args, ...args2) :
-    fn(...args));
+// Define function curry that accepts the length of the function
+// (amount of function arguments) and the function.
 
-// Use function curry to define function press
-// that allows to enter pin code by one character,
-// e.g. press('3')('4')('5')('6')
+const curry = (length, fn) => (...args) => null;
 
-const press = null;
+// Allows to enter pin code by one character,
+// Usage: press('3')('4')('5')('6')
+const press = curry(4, checkPin);
 
 // Set name for anonymous function (for tests).
 if (typeof press === 'function') {

From 5d35a4a6f23bc002e05585cbb1901af288e56ef8 Mon Sep 17 00:00:00 2001
From: Oleksandr Avoiants <shhavel@gmail.com>
Date: Mon, 6 Jan 2020 20:37:37 +0200
Subject: [PATCH 3/4] PR comments:

- use new hpw;
- remove setting names for anonymous functions for old hpw;
- remove unnecessary parentheses;
- refactor constructing current date string.
---
 Exercises/2-closure.js   | 12 +-----------
 Exercises/2-closure.test |  4 ++--
 Exercises/3-lambda.test  |  7 ++-----
 Exercises/4-bind.js      | 10 ----------
 Exercises/5-curry.js     |  7 +------
 Exercises/6-chaining.js  |  2 +-
 6 files changed, 7 insertions(+), 35 deletions(-)

diff --git a/Exercises/2-closure.js b/Exercises/2-closure.js
index 3f9aab2..d6f2435 100644
--- a/Exercises/2-closure.js
+++ b/Exercises/2-closure.js
@@ -1,7 +1,7 @@
 'use strict';
 
 const coffee = (volume, strength) =>
-  (`Coffee volume: ${volume}ml, strength: ${strength}`);
+  `Coffee volume: ${volume}ml, strength: ${strength}`;
 
 const defineCoffeeType = volume => strength => coffee(volume, strength);
 
@@ -12,14 +12,4 @@ const defineCoffeeType = volume => strength => coffee(volume, strength);
 const espresso = null;
 const americano = null;
 
-// Set names for anonymous functions (for tests).
-if (typeof espresso === 'function') {
-  Object.defineProperty(espresso, 'name',
-    { value: 'espresso', configurable: true });
-}
-if (typeof americano === 'function') {
-  Object.defineProperty(americano, 'name',
-    { value: 'americano', configurable: true });
-}
-
 module.exports = { espresso, americano };
diff --git a/Exercises/2-closure.test b/Exercises/2-closure.test
index f11cc0f..13fcfa1 100644
--- a/Exercises/2-closure.test
+++ b/Exercises/2-closure.test
@@ -1,4 +1,4 @@
-([{
+[{
   name: 'espresso',
   length: [30, 70],
   cases: [
@@ -13,4 +13,4 @@
     ['medium', 'Coffee volume: 150ml, strength: medium'],
     ['strong', 'Coffee volume: 150ml, strength: strong'],
   ]
-}])
+}]
diff --git a/Exercises/3-lambda.test b/Exercises/3-lambda.test
index d8dbc6e..4347aed 100644
--- a/Exercises/3-lambda.test
+++ b/Exercises/3-lambda.test
@@ -3,11 +3,8 @@
   length: [150, 400],
   test: tagDate => {
     {
-      const today = new Date();
-      const dd = String(today.getDate()).padStart(2, '0');
-      const mm = String(today.getMonth() + 1).padStart(2, '0');
-      const yyyy = today.getFullYear();
-      const expected = `[${yyyy}-${mm}-${dd}] Test`;
+      const date = new Date().toISOString().substring(0, 10);
+      const expected = `[${date}] Test`;
       const y = tagDate('Test');
       if (y !== expected) {
         throw new Error(`tagDate('Test') === ${y} expected: ${expected}`);
diff --git a/Exercises/4-bind.js b/Exercises/4-bind.js
index 4d869ba..1d1849a 100644
--- a/Exercises/4-bind.js
+++ b/Exercises/4-bind.js
@@ -22,14 +22,4 @@ const H = (exp, ...args) => {
 const average = null;
 const rootMeanSquare = null;
 
-// Set names for anonymous functions (for tests).
-if (typeof average === 'function') {
-  Object.defineProperty(average, 'name',
-    { value: 'average', configurable: true });
-}
-if (typeof rootMeanSquare === 'function') {
-  Object.defineProperty(rootMeanSquare, 'name',
-    { value: 'rootMeanSquare', configurable: true });
-}
-
 module.exports = { average, rootMeanSquare };
diff --git a/Exercises/5-curry.js b/Exercises/5-curry.js
index 48104f7..0b0f485 100644
--- a/Exercises/5-curry.js
+++ b/Exercises/5-curry.js
@@ -2,7 +2,7 @@
 
 // Check 4 digit pin.
 const checkPin = (...code) =>
-  (code.join('') === '4967');
+  code.join('') === '4967';
 
 // Define function curry that accepts the length of the function
 // (amount of function arguments) and the function.
@@ -13,9 +13,4 @@ const curry = (length, fn) => (...args) => null;
 // Usage: press('3')('4')('5')('6')
 const press = curry(4, checkPin);
 
-// Set name for anonymous function (for tests).
-if (typeof press === 'function') {
-  Object.defineProperty(press, 'name', { value: 'press', configurable: true });
-}
-
 module.exports = { press };
diff --git a/Exercises/6-chaining.js b/Exercises/6-chaining.js
index 9467775..ca3e7f5 100644
--- a/Exercises/6-chaining.js
+++ b/Exercises/6-chaining.js
@@ -2,7 +2,7 @@
 
 // Check 4 digit pin.
 const checkPin = (ch1, ch2, ch3, ch4) =>
-  ([ch1, ch2, ch3, ch4].join('') === '4967');
+  [ch1, ch2, ch3, ch4].join('') === '4967';
 
 // Impement function press
 // that allows to enter pin code by one character,

From e91b30a134e33311056a9dd5a21d4ea861da4dcd Mon Sep 17 00:00:00 2001
From: Oleksandr Avoiants <shhavel@gmail.com>
Date: Sat, 11 Jan 2020 02:26:06 +0200
Subject: [PATCH 4/4] PR comments. Move expected pin code out of checkPin
 function

---
 Exercises/5-curry.js    | 4 ++--
 Exercises/6-chaining.js | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Exercises/5-curry.js b/Exercises/5-curry.js
index 0b0f485..e175699 100644
--- a/Exercises/5-curry.js
+++ b/Exercises/5-curry.js
@@ -1,8 +1,8 @@
 'use strict';
 
 // Check 4 digit pin.
-const checkPin = (...code) =>
-  code.join('') === '4967';
+const EXPECTED_PIN = '4967';
+const checkPin = (...code) => code.join('') === EXPECTED_PIN;
 
 // Define function curry that accepts the length of the function
 // (amount of function arguments) and the function.
diff --git a/Exercises/6-chaining.js b/Exercises/6-chaining.js
index ca3e7f5..b0b2d26 100644
--- a/Exercises/6-chaining.js
+++ b/Exercises/6-chaining.js
@@ -1,8 +1,8 @@
 'use strict';
 
 // Check 4 digit pin.
-const checkPin = (ch1, ch2, ch3, ch4) =>
-  [ch1, ch2, ch3, ch4].join('') === '4967';
+const EXPECTED_PIN = '4967';
+const checkPin = (...code) => code.join('') === EXPECTED_PIN;
 
 // Impement function press
 // that allows to enter pin code by one character,