121 lines
No EOL
3.7 KiB
JavaScript
Executable file
121 lines
No EOL
3.7 KiB
JavaScript
Executable file
"use strict";
|
|
var __importDefault = (this && this.__importDefault) || function (mod) {
|
|
return (mod && mod.__esModule) ? mod : { "default": mod };
|
|
};
|
|
Object.defineProperty(exports, "__esModule", { value: true });
|
|
exports.generate = exports.compile = void 0;
|
|
var boolbase_1 = __importDefault(require("boolbase"));
|
|
/**
|
|
* Returns a function that checks if an elements index matches the given rule
|
|
* highly optimized to return the fastest solution.
|
|
*
|
|
* @param parsed A tuple [a, b], as returned by `parse`.
|
|
* @returns A highly optimized function that returns whether an index matches the nth-check.
|
|
* @example
|
|
*
|
|
* ```js
|
|
* const check = nthCheck.compile([2, 3]);
|
|
*
|
|
* check(0); // `false`
|
|
* check(1); // `false`
|
|
* check(2); // `true`
|
|
* check(3); // `false`
|
|
* check(4); // `true`
|
|
* check(5); // `false`
|
|
* check(6); // `true`
|
|
* ```
|
|
*/
|
|
function compile(parsed) {
|
|
var a = parsed[0];
|
|
// Subtract 1 from `b`, to convert from one- to zero-indexed.
|
|
var b = parsed[1] - 1;
|
|
/*
|
|
* When `b <= 0`, `a * n` won't be lead to any matches for `a < 0`.
|
|
* Besides, the specification states that no elements are
|
|
* matched when `a` and `b` are 0.
|
|
*
|
|
* `b < 0` here as we subtracted 1 from `b` above.
|
|
*/
|
|
if (b < 0 && a <= 0)
|
|
return boolbase_1.default.falseFunc;
|
|
// When `a` is in the range -1..1, it matches any element (so only `b` is checked).
|
|
if (a === -1)
|
|
return function (index) { return index <= b; };
|
|
if (a === 0)
|
|
return function (index) { return index === b; };
|
|
// When `b <= 0` and `a === 1`, they match any element.
|
|
if (a === 1)
|
|
return b < 0 ? boolbase_1.default.trueFunc : function (index) { return index >= b; };
|
|
/*
|
|
* Otherwise, modulo can be used to check if there is a match.
|
|
*
|
|
* Modulo doesn't care about the sign, so let's use `a`s absolute value.
|
|
*/
|
|
var absA = Math.abs(a);
|
|
// Get `b mod a`, + a if this is negative.
|
|
var bMod = ((b % absA) + absA) % absA;
|
|
return a > 1
|
|
? function (index) { return index >= b && index % absA === bMod; }
|
|
: function (index) { return index <= b && index % absA === bMod; };
|
|
}
|
|
exports.compile = compile;
|
|
/**
|
|
* Returns a function that produces a monotonously increasing sequence of indices.
|
|
*
|
|
* If the sequence has an end, the returned function will return `null` after
|
|
* the last index in the sequence.
|
|
*
|
|
* @param parsed A tuple [a, b], as returned by `parse`.
|
|
* @returns A function that produces a sequence of indices.
|
|
* @example <caption>Always increasing (2n+3)</caption>
|
|
*
|
|
* ```js
|
|
* const gen = nthCheck.generate([2, 3])
|
|
*
|
|
* gen() // `1`
|
|
* gen() // `3`
|
|
* gen() // `5`
|
|
* gen() // `8`
|
|
* gen() // `11`
|
|
* ```
|
|
*
|
|
* @example <caption>With end value (-2n+10)</caption>
|
|
*
|
|
* ```js
|
|
*
|
|
* const gen = nthCheck.generate([-2, 5]);
|
|
*
|
|
* gen() // 0
|
|
* gen() // 2
|
|
* gen() // 4
|
|
* gen() // null
|
|
* ```
|
|
*/
|
|
function generate(parsed) {
|
|
var a = parsed[0];
|
|
// Subtract 1 from `b`, to convert from one- to zero-indexed.
|
|
var b = parsed[1] - 1;
|
|
var n = 0;
|
|
// Make sure to always return an increasing sequence
|
|
if (a < 0) {
|
|
var aPos_1 = -a;
|
|
// Get `b mod a`
|
|
var minValue_1 = ((b % aPos_1) + aPos_1) % aPos_1;
|
|
return function () {
|
|
var val = minValue_1 + aPos_1 * n++;
|
|
return val > b ? null : val;
|
|
};
|
|
}
|
|
if (a === 0)
|
|
return b < 0
|
|
? // There are no result — always return `null`
|
|
function () { return null; }
|
|
: // Return `b` exactly once
|
|
function () { return (n++ === 0 ? b : null); };
|
|
if (b < 0) {
|
|
b += a * Math.ceil(-b / a);
|
|
}
|
|
return function () { return a * n++ + b; };
|
|
}
|
|
exports.generate = generate;
|
|
//# sourceMappingURL=compile.js.map
|