added binomial_coefficient.js, count_decimal_digits.js, factorial.js,…

… multiply_range.js, round.js, truncate_decimal.js

README.md

@@ -16,16 +16,19 @@
 The following functions are supported:
 - [absolute](#absolute)
 - [add](#add)
+- [binomial_coefficient](#binomial_coefficient)
 - [ceil](#ceil)
 - [compare](#compare)
 - [divide](#divide)
+- [factorial](#factorial)
 - [floor](#floor)
 - [max](#max)
 - [mean](#mean)
 - [min](#min)
 - [multiply](#multiply)
 - [pow](#pow)
 - [remainder](#remainder)
+- [round](#round)
 - [sign](#sign)
 - [sort](#sort)
 - [subtract](#subtract)
@@ -67,6 +70,15 @@ add("0.1", "0.2"); // 0.1 + 0.2
 "0.3"
 ```
 
+### binomial_coefficient
+```js
+import binomial_coefficient from "preciso/binomial_coefficient.js";
+
+// 7 choose 3
+binomial_coefficient("7", "3")
+"35"
+```
+
 ### compare
 ```js
 import compare from "preciso/compare.js";
@@ -102,6 +114,20 @@ divide("-714.7008086132632", "8135.725531"); // -714.7008086132632 / 8135.725531
 '-0.0878472123832102762218908980055167989417759034280282678823325216230183564682007707223868489179001533'
 ```
 
+### factorial
+```js
+import factorial from "preciso/factorial.js";
+
+factorial("0");
+"1"
+
+factorial("3");
+"6"
+
+factorial("10");
+"3628800"
+```
+
 ### floor
 ```js
 import floor from "preciso/floor.js";
@@ -177,6 +203,21 @@ remainder("-0.5", "2"); // -0.5 % 2
 "-0.5"
 ```
 
+### round
+```js
+import round from "preciso/round.js";
+
+round("0.99")
+"1"
+
+round("0.12345");
+"0"
+
+// round to the specified number of digits
+round("0.12345", { digits: 2 })
+"0.12"
+```
+
 ### sign
 ```js
 import sign from "preciso/subtract.js";

absolute.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const clean = require("./clean.js");
 
 function absolute(n) {

add.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const compare_positive = require("./compare_positive.js");
 const clean = require("./clean.js");
 const long_addition = require("./long_addition.js");

binomial_coefficient.js

@@ -0,0 +1,31 @@
+"use strict";
+
+const clean = require("./clean.js");
+const compare_positive = require("./compare_positive.js");
+const factorial = require("./factorial.js");
+const long_addition = require("./long_addition.js");
+const long_subtraction = require("./long_subtraction.js");
+const long_division = require("./long_division.js");
+const multiply_range = require("./multiply_range.js");
+
+function binomial_coefficient(n, k) {
+  n = clean(n);
+  k = clean(k);
+
+  switch (compare_positive(n, k)) {
+    case "=":
+      return "1";
+    case ">": {
+      const diff = long_subtraction(n, k);
+      const numerator = multiply_range(long_addition(k, "1"), n);
+      const denominator = factorial(diff);
+      return long_division(numerator, denominator);
+    }
+    case "<": {
+      throw new Error("[binominal_coefficient] unsupported");
+    }
+  }
+}
+
+module.exports = binomial_coefficient;
+module.exports.default = binomial_coefficient;

ceil.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const absolute = require("./absolute.js");
 const clean = require("./clean.js");
 const long_addition = require("./long_addition.js");

clean.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const expand = require("./expand.js");
 
 module.exports = function clean(n) {
@@ -16,5 +18,7 @@ module.exports = function clean(n) {
   // should improve this, so it identifies zero earlier
   if (n === "") n = "0";
 
+  if (n === "-0") n = "0";
+
   return n;
 };

compare.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const clean = require("./clean.js");
 const compare_positive = require("./compare_positive.js");
 

compare_positive.js

@@ -1,4 +1,4 @@
-const clean = require("./clean.js");
+"use strict";
 
 // given:
 //  - a and b are positive numbers

constants.js

@@ -1,3 +1,5 @@
+"use strict";
+
 // Internet Explorer doesn't support Number.MAX_SAFE_INTEGER
 // so we just define the constant ourselves
 const MAX_SAFE_INTEGER = 9007199254740991;

count_decimal_digits.js

@@ -0,0 +1,17 @@
+"use strict";
+
+const clean = require("./clean.js");
+
+function count_decimal_digits(n) {
+  n = clean(n);
+
+  const i = n.indexOf(".");
+
+  // n is an integer
+  if (i === -1) return "0";
+
+  return (n.length - i - 1).toString();
+}
+
+module.exports = count_decimal_digits;
+module.exports.default = count_decimal_digits;

divide.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const absolute = require("./absolute.js");
 const clean = require("./clean.js");
 const long_division = require("./long_division.js");

expand.js

@@ -1,3 +1,5 @@
+"use strict";
+
 // convert exponential notation to normal string
 // not optimized yet and no support for big numbers
 function expand(n) {
@@ -36,7 +38,7 @@ function expand(n) {
     return sign + result;
   } else if (normshift < 0) {
     // need to add zeros in decimal places
-    result = "0.";
+    let result = "0.";
     for (let i = 0; i > normshift; i--) result += "0";
     result += base;
     return sign + result;

factorial.js

@@ -0,0 +1,11 @@
+"use strict";
+
+const multiply_range = require("./multiply_range.js");
+
+function factorial(n) {
+  if (n === "0") return "1";
+  return multiply_range("1", n);
+}
+
+module.exports = factorial;
+module.exports.default = factorial;

floor.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const absolute = require("./absolute.js");
 const clean = require("./clean.js");
 const long_addition = require("./long_addition.js");

is_factorial.js

@@ -0,0 +1,8 @@
+"use strict";
+
+function is_factorial(n) {
+  return !!n.match(/^\d+!$/i);
+}
+
+module.exports = is_factorial;
+module.exports.default = is_factorial;

is_infinity.js

@@ -1,3 +1,8 @@
-module.exports = function is_infinity(n) {
+"use strict";
+
+function is_infinity(n) {
   return !!n.match(/^(|-|\+)inf(inity)?$/i);
-};
+}
+
+module.exports = is_infinity;
+module.exports.default = is_infinity;

is_integer.js

@@ -1,8 +1,13 @@
+"use strict";
+
 const clean = require("./clean.js");
 const is_infinity = require("./is_infinity.js");
 
-module.exports = function is_integer(n) {
+function is_integer(n) {
   if (is_infinity(n)) return false;
   n = clean(n);
   return !n.includes(".");
-};
+}
+
+module.exports = is_integer;
+module.exports.default = is_integer;

is_negative.js

@@ -0,0 +1,11 @@
+"use strict";
+
+const clean = require("./clean");
+
+function is_negative(n) {
+  n = clean(n);
+  return n[0] === "-";
+}
+
+module.exports = is_negative;
+module.exports.default = is_negative;

is_negative_infinity.js

@@ -1,3 +1,8 @@
-module.exports = function is_negative_infinity(n) {
+"use strict";
+
+function is_negative_infinity(n) {
   return !!n.match(/^-inf(inity)?$/i);
-};
+}
+
+module.exports = is_negative_infinity;
+module.exports.default = is_negative_infinity;

is_positive_infinity.js

@@ -1,3 +1,8 @@
-module.exports = function is_positive_infinity(n) {
+"use strict";
+
+function is_positive_infinity(n) {
   return !!n.match(/^\+?inf(inity)?$/i);
-};
+}
+
+module.exports = is_positive_infinity;
+module.exports.default = is_positive_infinity;

is_zero.js

@@ -1,3 +1,8 @@
-module.exports = function is_zero(n) {
+"use strict";
+
+function is_zero(n) {
   return /^[-+]?0(\.0+)?(e[\.\d]+)?$/.test(n);
-};
+}
+
+module.exports = is_zero;
+module.exports.default = is_zero;

long_addition.js

@@ -1,7 +1,9 @@
+"use strict";
+
 const { MAX_SAFE_INTEGER_LENGTH } = require("./constants.js");
 
 // assumes both numbers are positive numbers
-module.exports = function long_addition(a, b) {
+function long_addition(a, b) {
   const alen = a.length;
   const blen = b.length;
 
@@ -86,4 +88,7 @@ module.exports = function long_addition(a, b) {
   if (result[0] === ".") result = "0" + result;
 
   return result;
-};
+}
+
+module.exports = long_addition;
+module.exports.default = long_addition;

long_division.js

@@ -1,11 +1,12 @@
+"use strict";
+
 const compare_positive = require("./compare_positive.js");
 const add = require("./add.js");
-const multiply = require("./multiply.js");
 const subtract = require("./subtract.js");
 const round_last_decimal = require("./round_last_decimal.js");
 
 // given dividend and divisor are positive numberical strings
-module.exports = function long_division(dividend, divisor, { max_decimal_digits = 100, ellipsis = false } = {}) {
+function long_division(dividend, divisor, { max_decimal_digits = 100, ellipsis = false } = {}) {
   // remove unnecessary starting zeros
   // ex: 0.5 => .5
   if (dividend[0] === "0") dividend = dividend.substring(1);
@@ -195,4 +196,7 @@ module.exports = function long_division(dividend, divisor, { max_decimal_digits
   if (quotient[0] === ".") quotient = "0" + quotient;
 
   return quotient;
-};
+}
+
+module.exports = long_division;
+module.exports.default = long_division;

long_multiplication.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const { MAX_SAFE_INTEGER_LENGTH } = require("./constants.js");
 
 const CHUNK_SIZE = 15;
@@ -9,7 +11,7 @@ const CHUNK_SIZE = 15;
  * @returns {String} product - result of multiplying a with b
  */
 
-module.exports = function long_multiplication(a, b) {
+function long_multiplication(a, b) {
   if (a === "0" || b === "0") return "0";
 
   const top_index_of_dot = a.indexOf(".");
@@ -132,4 +134,7 @@ module.exports = function long_multiplication(a, b) {
   }
 
   return result;
-};
+}
+
+module.exports = long_multiplication;
+module.exports.default = long_multiplication;

long_subtraction.js

@@ -1,3 +1,5 @@
+"use strict";
+
 // const lookup = {};
 // const vals = [undefined, 0, 1, 2, 3, 4, 5, 6, 8, 9];
 // vals.forEach(top => {
@@ -11,7 +13,7 @@ const { MAX_SAFE_INTEGER_LENGTH } = require("./constants.js");
 
 // assumes (1) both a and b are positive numbers
 // and (2) a is larger than b
-module.exports = function long_subtraction(a, b) {
+function long_subtraction(a, b) {
   const alen = a.length;
   const blen = b.length;
 
@@ -141,4 +143,7 @@ module.exports = function long_subtraction(a, b) {
   if (result[0] === ".") result = "0" + result;
 
   return result;
-};
+}
+
+module.exports = long_subtraction;
+module.exports.default = long_subtraction;

max.js

@@ -1,3 +1,5 @@
+"use strict";
+
 const clean = require("./clean.js");
 const compare = require("./compare.js");