Add Computus in Javascript and Typescript

CONTRIBUTORS.md

@@ -57,4 +57,5 @@ This file lists everyone, who contributed to this repo and wanted to show up her
 - Delphi1024
 - ntindle
 - Mahdi Sarikhani
-- Ridham177
+- Ridham177
+- Hugo Salou

book.json

@@ -193,8 +193,8 @@
         {
           "lang": "ps1",
           "name": "PowerShell"
-	},
-	{
+        },
+        {
           "lang": "v",
           "name": "Vlang"
         },
@@ -217,6 +217,10 @@
         {
           "lang": "coco",
           "name": "Coconut"
+        },
+        {
+          "lang": "dart",
+          "name": "Dart"
         }
       ]
     }

contents/computus/code/dart/gauss_easter.dart

@@ -0,0 +1,63 @@
+String computus(int year, {bool servois = false}) {
+  // Year's position in metonic cycle
+  final a = year % 19;
+
+  // Century index
+  final k = (year / 100).floor();
+
+  // Shift of metonic cycle, add a day offset every 300 years
+  final p = ((13 + 8 * k) / 25).floor();
+
+  // Correction for non-observed leap days
+  final q = (k / 4).floor();
+
+  // Correction to starting point of calculation each century
+  final M = (15 - p + k - q) % 30;
+
+  // Number of days from March 21st until the full moon
+  final d = (19 * a + M) % 30;
+
+  // Returning if user wants value for Servois' table
+  if (servois) {
+    return ((21 + d) % 31).toString();
+  }
+
+  // Finding the next Sunday
+  // Century-based offset in weekly calculation
+  final N = (4 + k - q) % 7;
+
+  // Correction for leap days
+  final b = year % 4;
+  final c = year % 7;
+
+  // Days from d to next Sunday
+  var e = (2 * b + 4 * c + 6 * d + N) % 7;
+
+  // Historical corrections for April 26 and 25
+  if (e == 6) {
+    if (d == 29 || (d == 28 && a > 10)) {
+      e = -1;
+    }
+  }
+
+  // Determination of the correct month for Easter
+  if (22 + d + e > 31) {
+    return 'April ${d + e - 9}';
+  } else {
+    return 'March ${22 + d + e}';
+  }
+}
+
+void main() {
+  print("The following are the dates of the Paschal full moon (using Servois " +
+      "notation) and the date of Easter for 2020-2030 AD:");
+
+  print("Year\tServois number\tEaster");
+
+  for (var year = 2020; year <= 2030; year++) {
+    final servoisNumber = computus(year, servois: true);
+    final easterDate = computus(year);
+
+    print('$year\t$servoisNumber\t\t$easterDate');
+  }
+}

contents/computus/code/javascript/gauss_easter.js

@@ -0,0 +1,91 @@
+/**
+ * In this code, the modulus operator is used.
+ * However, this operator in javascript/typescript doesn't support negative numbers.
+ * So, where there may be negative numbers, the function mod is used.
+ * This function gives the modulo of any relative number a
+ */
+
+/**
+ * @param {number} a
+ * @param {number} b
+ * @returns {number}
+ */
+function mod(a, b) {
+  if (a < 0) return mod(a + b, b);
+  else return a % b;
+}
+
+/**
+ * @param {number} year
+ * @param {boolean} [servois=false]
+ * @returns {string}
+ */
+function computus(year, servois = false) {
+  // Year's position in metonic cycle
+  const a = year % 19;
+
+  // Century index
+  const k = Math.floor(year / 100);
+
+  // Shift of metonic cycle, add a day offset every 300 years
+  const p = Math.floor((13 + 8 * k) / 25);
+
+  // Correction for non-observed leap days
+  const q = Math.floor(k / 4);
+
+  // Correction to starting point of calculation each century
+  const M = mod(15 - p + k - q, 30);
+
+  // Number of days from March 21st until the full moon
+  const d = (19 * a + M) % 30;
+
+  // Returning if user wants value for Servois' table
+  if (servois) {
+    return ((21 + d) % 31).toString();
+  }
+
+  // Finding the next Sunday
+  // Century-based offset in weekly calculation
+  const N = mod(4 + k - q, 7);
+
+  // Correction for leap days
+  const b = year % 4;
+  const c = year % 7;
+
+  // Days from d to next Sunday
+  let e = (2 * b + 4 * c + 6 * d + N) % 7;
+
+  // Historical corrections for April 26 and 25
+  if (e === 6) {
+    if (d === 29 || (d === 28 && a > 10)) {
+      e = -1;
+    }
+  }
+
+  // Determination of the correct month for Easter
+  if (22 + d + e > 31) {
+    return `April ${d + e - 9}`;
+  } else {
+    return `March ${22 + d + e}`;
+  }
+}
+
+console.log(
+  "The following are the dates of the Paschal full moon (using Servois " +
+    "notation) and the date of Easter for 2020-2030 AD:"
+);
+
+const values = [];
+
+for (let year = 2020; year <= 2030; year++) {
+  const servoisNumber = computus(year, true);
+  const easterDate = computus(year);
+
+  // Creation of an object to be displayed as a line in the output table
+  values[year] = {
+    "servois number": +servoisNumber,
+    easter: easterDate,
+  };
+}
+
+console.table(values);

contents/computus/code/typescript/gauss_easter.ts

@@ -0,0 +1,91 @@
+/**
+ * In this code, the modulus operator is used.
+ * However, this operator in javascript/typescript doesn't support negative numbers.
+ * So, where there may be negative numbers, the function mod is used.
+ * This function gives the modulo of any relative number a
+ */
+
+function mod(a: number, b: number): number {
+  if (a < 0) {
+    return mod(a + b, b);
+  } else {
+    return a % b;
+  }
+}
+function computus(year: number, servois: boolean = false): string {
+  // Year's position in metonic cycle
+  const a: number = year % 19;
+
+  // Century index
+  const k: number = Math.floor(year / 100);
+
+  // Shift of metonic cycle, add a day offset every 300 years
+  const p: number = Math.floor((13 + 8 * k) / 25);
+
+  // Correction for non-observed leap days
+  const q: number = Math.floor(k / 4);
+
+  // Correction to starting point of calculation each century
+  const M: number = mod(15 - p + k - q, 30);
+
+  // Number of days from March 21st until the full moon
+  const d: number = (19 * a + M) % 30;
+
+  // Returning if user wants value for Servois' table
+  if (servois) {
+    return ((21 + d) % 31).toString();
+  }
+
+  // Finding the next Sunday
+  // Century-based offset in weekly calculation
+  const N: number = mod(4 + k - q, 7);
+
+  // Correction for leap days
+  const b: number = year % 4;
+  const c: number = year % 7;
+
+  // Days from d to next Sunday
+  let e: number = (2 * b + 4 * c + 6 * d + N) % 7;
+
+  // Historical corrections for April 26 and 25
+  if (e === 6) {
+    if (d === 29 || (d === 28 && a > 10)) {
+      e = -1;
+    }
+  }
+
+  // Determination of the correct month for Easter
+  if (22 + d + e > 31) {
+    return `April ${d + e - 9}`;
+  } else {
+    return `March ${22 + d + e}`;
+  }
+}
+
+console.log(
+  "The following are the dates of the Paschal full moon (using Servois " +
+    "notation) and the date of Easter for 2020-2030 AD:"
+);
+
+// Type of a line in the output table
+interface IOutputLine {
+  "servois number": number;
+  easter: string;
+}
+
+const values: IOutputLine[] = [];
+
+for (let year = 2020; year <= 2030; year++) {
+  const servoisNumber: string = computus(year, true);
+  const easterDate: string = computus(year);
+
+  // Creation of an object to be displayed as a line in the output table
+  const line: IOutputLine = {
+    "servois number": +servoisNumber,
+    easter: easterDate,
+  };
+
+  values[year] = line;
+}
+
+console.table(values);

contents/computus/computus.md

@@ -322,6 +322,12 @@ For now, we have the code outputting a tuple of $$d$$ and $$e$$, so users can us
 [import, lang:"nim"](code/nim/gauss_easter.nim)
 {% sample lang="scala" %}
 [import, lang:"scala"](code/scala/gauss_easter.scala)
+{% sample lang="dart" %}
+[import, lang:"dart"](code/dart/gauss_easter.dart)
+{% sample lang="javascript" %}
+[import, lang:"javascript"](code/javascript/gauss_easter.js)
+{% sample lang="typescript" %}
+[import, lang:"typescript"](code/typescript/gauss_easter.ts)
 {% endmethod %}