Merge branch 'master' into any-all-none

This commit is contained in:
Angelos Chalaris
2018-02-14 13:21:33 +02:00
committed by GitHub
26 changed files with 543 additions and 5 deletions

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### approximatelyEqual
Checks if two numbers are approximately equal to each other.
Use `Math.abs()` to compare the absolute difference of the two values to `epsilon`.
Omit the third parameter, `epsilon`, to use a default value of `0.001`.
```js
const approximatelyEqual = (v1, v2, epsilon = 0.001) => Math.abs(v1 - v2) < epsilon;
```
```js
approximatelyEqual(Math.PI / 2.0, 1.5708); // true
```

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### bifurcate
Splits values into two groups. If an element in `filter` is truthy, the corresponding element in the collection belongs to the first group; otherwise, it belongs to the second group.
Use `Array.reduce()` and `Array.push()` to add elements to groups, based on `filter`.
```js
const bifurcate = (arr, filter) =>
arr.reduce((acc, val, i) => (acc[filter[i] ? 0 : 1].push(val), acc), [[], []]);
```
```js
bifurcate(['beep', 'boop', 'foo', 'bar'], [true, true, false, true]); // [ ['beep', 'boop', 'bar'], ['foo'] ]
```

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### bifurcateBy
Splits values into two groups according to a predicate function, which specifies which group an element in the input collection belongs to. If the predicate function returns a truthy value, the collection element belongs to the first group; otherwise, it belongs to the second group.
Use `Array.reduce()` and `Array.push()` to add elements to groups, based on the value returned by `fn` for each element.
```js
const bifurcateBy = (arr, fn) =>
arr.reduce((acc, val, i) => (acc[fn(val, i) ? 0 : 1].push(val), acc), [[], []]);
```
```js
bifurcateBy(['beep', 'boop', 'foo', 'bar'], x => x[0] === 'b'); // [ ['beep', 'boop', 'bar'], ['foo'] ]
```

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### binomialCoefficient
Evaluates the binomial coefficient of two integers `n` and `k`.
Use `Number.isNaN()` to check if any of the two values is `NaN`.
Check if `k` is less than `0`, greater than or equal to `n`, equal to `1` or `n - 1` and return the appropriate result.
Check if `n - k` is less than `k` and switch their values accordingly.
Loop from `2` through `k` and calculate the binomial coefficient.
Use `Math.round()` to account for rounding errors in the calculation.
```js
const binomialCoefficient = (n, k) => {
if (Number.isNaN(n) || Number.isNaN(k)) return NaN;
if (k < 0 || k > n) return 0;
if (k === 0 || k === n) return 1;
if (k === 1 || k === n - 1) return n;
if (n - k < k) k = n - k;
let res = n;
for (let j = 2; j <= k; j++) res *= (n - j + 1) / j;
return Math.round(res);
};
```
```js
binomialCoefficient(8, 2); // 28
```

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### degreesToRads
Converts an angle from degrees to radians.
Use `Math.PI` and the degree to radian formula to convert the angle from degrees to radians.
```js
const degreesToRads = deg => deg * Math.PI / 180.0;
```
```js
degreesToRads(90.0); // ~1.5708
```

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### radsToDegrees
Converts an angle from radians to degrees.
Use `Math.PI` and the radian to degree formula to convert the angle from radians to degrees.
```js
const radsToDegrees = rad => rad * 180.0 / Math.PI;
```
```js
radsToDegrees(Math.PI / 2); // 90
```

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### uncurry
Uncurries a function up to depth `n`.
Return a variadic function.
Use `Array.reduce()` on the provided arguments to call each subsequent curry level of the function.
If the `length` of the provided arguments is less than `n` throw an error.
Otherwise, call `fn` with the proper amount of arguments, using `Array.slice(0, n)`.
Omit the second argument, `n`, to uncurry up to depth `1`.
```js
const uncurry = (fn, n = 1) => (...args) => {
const next = acc => args => args.reduce((x, y) => x(y), acc);
if (n > args.length) throw new RangeError('Arguments too few!');
return next(fn)(args.slice(0, n));
};
```
```js
const add = x => y => z => x + y + z;
const uncurriedAdd = uncurry(add, 3);
uncurriedAdd(1, 2, 3); // 6
```