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round_rational.js
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round_rational.js
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"use strict";
const clean = require("./clean.js");
const count_decimal_digits = require("./count_decimal_digits.js");
const absolute = require("./absolute.js");
const is_negative = require("./is_negative.js");
const round_last_decimal = require("./round_last_decimal.js");
const UP = ["5", "6", "7", "8", "9"];
function round_rational(n, { digits = 0 } = { digits: 0 }) {
n = clean(n);
const orig = n;
const sign = is_negative(n) ? "-" : "";
// convert to positive because
// round_last_decimal only works on positive decimals
n = absolute(n);
const idec = n.indexOf(".");
// integer, already rounded
if (idec === -1) return orig;
// decimal, but already rounded enough
if (count_decimal_digits(n) <= digits) return orig;
const v = n[idec + digits + 1];
if (UP.includes(v)) {
const clip = n.substring(0, idec + digits + 2);
return sign + round_last_decimal(clip);
} else if (digits === 0) {
return sign + n.substring(0, idec);
} else {
const clip = n.substring(0, idec + digits + 1);
return sign + clip;
}
}
module.exports = round_rational;
module.exports.default = round_rational;