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Define pick quantum #115

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merged 7 commits into from
Sep 3, 2024
Merged

Define pick quantum #115

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35b9cde
WIP
jessealama Jul 1, 2024
79a0270
WIP
jessealama Jul 2, 2024
70be76b
Get subtraction and constructor tests to work
jessealama Jul 2, 2024
c5ee874
Fix tests
jessealama Sep 3, 2024
1523c88
Remove dead code
jessealama Sep 3, 2024
5dc47b9
Remove dead code
jessealama Sep 3, 2024
c827d60
Merge branch 'main' into define-pick-quantum
jessealama Sep 3, 2024
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15 changes: 5 additions & 10 deletions src/Decimal.mts
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Original file line number Diff line number Diff line change
Expand Up @@ -78,16 +78,6 @@ export class Decimal {
throw new RangeError("The quantum cannot be negative zero.");
}

if (v instanceof Rational) {
let scaledV = v.scale10(0 - q);

if (!scaledV.isInteger()) {
throw new RangeError(
`Scaled value is not an integer (v = ${v}, q = ${q})`
);
}
}

this.cohort = v;
this.quantum = q;
}
Expand All @@ -107,4 +97,9 @@ export class Decimal {
let c = v.scale10(0 - q);
return c.numerator;
}

isNegative(): boolean {
let v = this.cohort as Rational;
return v.isNegative;
}
}
163 changes: 109 additions & 54 deletions src/Decimal128.mts
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Original file line number Diff line number Diff line change
Expand Up @@ -13,18 +13,22 @@
* @author Jesse Alama <jesse@igalia.com>
*/

import { RoundingMode, ROUNDING_MODES } from "./common.mjs";
import {
RoundingMode,
ROUNDING_MODES,
ROUNDING_MODE_HALF_EVEN,
ROUNDING_MODE_TRUNCATE,
} from "./common.mjs";
import { Rational } from "./Rational.mjs";
import { Decimal } from "./Decimal.mjs";

const EXPONENT_MIN = -6176;
const NORMAL_EXPONENT_MIN = -6143;
const EXPONENT_MAX = 6111;
const NORMAL_EXPONENT_MAX = 6144;
const MAX_SIGNIFICANT_DIGITS = 34;

const bigTen = BigInt(10);
const bigOne = BigInt(1);
const ratOne = new Rational(1n, 1n);
const ratTen = new Rational(10n, 1n);

type NaNValue = "NaN";
type InfiniteValue = "Infinity" | "-Infinity";
Expand All @@ -35,55 +39,68 @@ type Decimal128Value = NaNValue | InfiniteValue | FiniteValue;
const NAN = "NaN";
const POSITIVE_INFINITY = "Infinity";
const NEGATIVE_INFINITY = "-Infinity";
const TEN_MAX_EXPONENT = new Rational(
bigTen ** BigInt(MAX_SIGNIFICANT_DIGITS),
bigOne
);
const TEN_MAX_EXPONENT = bigTen ** BigInt(MAX_SIGNIFICANT_DIGITS);

function pickQuantum(
d: "0" | "-0" | Rational,
preferredQuantum: number
): number {
if (preferredQuantum < EXPONENT_MIN) {
return EXPONENT_MIN;
}

if (preferredQuantum > EXPONENT_MAX) {
return EXPONENT_MAX;
}

return preferredQuantum;
}

function adjustDecimal128(v: Rational, q: number): Decimal {
if (v.isNegative) {
return adjustDecimal128(v.negate(), q).negate();
function adjustDecimal128(d: Decimal): Decimal128Value {
let v = d.cohort;
let q = d.quantum;

if (v === "0" || v === "-0") {
return new Decimal({ cohort: v, quantum: pickQuantum(v, q) });
}

let x = new Decimal({ cohort: v, quantum: q });
if (d.isNegative()) {
let adjusted = adjustDecimal128(d.negate());

if (v.scale10(0 - q).cmp(TEN_MAX_EXPONENT) <= 0) {
return x;
if (adjusted === "Infinity") {
return "-Infinity";
}

return (adjusted as Decimal).negate();
}

if (v.isInteger()) {
let tenth = v.scale10(-1);
if (tenth.isInteger()) {
return adjustDecimal128(tenth, q + 1);
}
let coef = d.coefficient();

throw new RangeError("Integer too large");
if (coef <= TEN_MAX_EXPONENT && EXPONENT_MIN <= q && q <= EXPONENT_MAX) {
return d;
}

let c = x.cohort as Rational;
let cAsString = c.toFixed(Infinity);
let [integerPart, fractionalPart] = cAsString.split(/[.]/);
let renderedCohort = v.toFixed(Infinity);
let [integerPart, _] = renderedCohort.split(/[.]/);

if (integerPart === "0") {
integerPart = "";
}

if (integerPart.length > MAX_SIGNIFICANT_DIGITS) {
throw new RangeError("Integer part too large");
return "Infinity";
}

let scaledSig = c.scale10(MAX_SIGNIFICANT_DIGITS - integerPart.length);
let scaledSig = v.scale10(MAX_SIGNIFICANT_DIGITS - integerPart.length);
let rounded = scaledSig.round(0, "halfEven");
let rescaled = rounded.scale10(
0 - MAX_SIGNIFICANT_DIGITS + integerPart.length
);

if (rescaled.isZero()) {
return new Decimal({ cohort: "0", quantum: pickQuantum("0", q) });
}

let rescaledAsString = rescaled.toFixed(Infinity);
return new Decimal(rescaledAsString);
}
Expand All @@ -98,27 +115,9 @@ function validateConstructorData(x: Decimal128Value): Decimal128Value {
let v = val.cohort;
let q = val.quantum;

if (q > EXPONENT_MAX) {
if (v === "0" || v === "-0") {
return new Decimal({ cohort: v, quantum: EXPONENT_MAX });
}

throw new RangeError(`Quantum too big (${q})`);
}
let d = new Decimal({ cohort: v, quantum: q });

if (q < EXPONENT_MIN) {
if (v === "0" || v === "-0") {
return new Decimal({ cohort: v, quantum: EXPONENT_MIN });
}

throw new RangeError(`Quantum too small (${q})`);
}

if (v === "0" || v === "-0") {
return x;
}

return adjustDecimal128(v, q);
return adjustDecimal128(d);
}

function handleDecimalNotation(s: string): Decimal128Value {
Expand Down Expand Up @@ -157,14 +156,6 @@ function handleDecimalNotation(s: string): Decimal128Value {
return new Decimal(s);
}

export const ROUNDING_MODE_CEILING: RoundingMode = "ceil";
export const ROUNDING_MODE_FLOOR: RoundingMode = "floor";
export const ROUNDING_MODE_TRUNCATE: RoundingMode = "trunc";
export const ROUNDING_MODE_HALF_EVEN: RoundingMode = "halfEven";
export const ROUNDING_MODE_HALF_EXPAND: RoundingMode = "halfExpand";

const ROUNDING_MODE_DEFAULT: RoundingMode = ROUNDING_MODE_HALF_EVEN;

export class Decimal128 {
private readonly d: Decimal | undefined = undefined;
private readonly _isNaN: boolean = false;
Expand Down Expand Up @@ -990,7 +981,7 @@ export class Decimal128 {
*/
round(
numDecimalDigits: number = 0,
mode: RoundingMode = ROUNDING_MODE_DEFAULT
mode: RoundingMode = ROUNDING_MODE_HALF_EVEN
): Decimal128 {
if (!ROUNDING_MODES.includes(mode)) {
throw new RangeError(`Invalid rounding mode "${mode}"`);
Expand Down Expand Up @@ -1092,6 +1083,70 @@ export class Decimal128 {
let q = this.divide(d).round(0, ROUNDING_MODE_TRUNCATE);
return this.subtract(d.multiply(q));
}

isNormal(): boolean {
if (this.isNaN()) {
throw new RangeError("Cannot determine whether NaN is normal");
}

if (!this.isFinite()) {
throw new RangeError(
"Only finite numbers can be said to be normal or not"
);
}

if (this.isZero()) {
throw new RangeError(
"Only non-zero numbers can be said to be normal or not"
);
}

let exp = this.exponent();
return exp >= NORMAL_EXPONENT_MIN && exp <= NORMAL_EXPONENT_MAX;
}

isSubnormal(): boolean {
if (this.isNaN()) {
throw new RangeError("Cannot determine whether NaN is subnormal");
}

if (!this.isFinite()) {
throw new RangeError(
"Only finite numbers can be said to be subnormal or not"
);
}

let exp = this.exponent();
return exp < NORMAL_EXPONENT_MIN;
}

truncatedExponent(): number {
if (this.isZero() || this.isSubnormal()) {
return NORMAL_EXPONENT_MIN;
}

return this.exponent();
}

scaledSignificand(): bigint {
if (this.isNaN()) {
throw new RangeError("NaN does not have a scaled significand");
}

if (!this.isFinite()) {
throw new RangeError("Infinity does not have a scaled significand");
}

if (this.isZero()) {
return 0n;
}

let v = this.cohort() as Rational;
let te = this.truncatedExponent();
let ss = v.scale10(MAX_SIGNIFICANT_DIGITS - 1 - te);

return ss.numerator;
}
}

Decimal128.prototype.valueOf = function () {
Expand Down
10 changes: 6 additions & 4 deletions src/Rational.mts
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Original file line number Diff line number Diff line change
Expand Up @@ -163,10 +163,6 @@ export class Rational {
);
}

public isInteger(): boolean {
return this.denominator === 1n;
}

public negate(): Rational {
if (this.isNegative) {
return new Rational(this.numerator, this.denominator);
Expand Down Expand Up @@ -244,6 +240,12 @@ export class Rational {
}

if (this.numerator === zero) {
if (Infinity === n) {
throw new RangeError(
"Cannot enumerate infinite decimal places of zero"
);
}

return "0" + "." + "0".repeat(n);
}

Expand Down
4 changes: 2 additions & 2 deletions tests/Decimal128/add.test.js
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Expand Up @@ -50,10 +50,10 @@ describe("addition", () => {
expect(big.add(one).toString()).toStrictEqual(one.add(big).toString());
});
test("two plus big is not OK (too many significant digits)", () => {
expect(() => two.add(big)).toThrow(RangeError);
expect(two.add(big).toString()).toStrictEqual("Infinity");
});
test("big plus two is not OK (too many significant digits)", () => {
expect(() => big.add(two)).toThrow(RangeError);
expect(big.add(two).toString()).toStrictEqual("Infinity");
});
describe("non-normalized", () => {
test("one point zero plus one point zero", () => {
Expand Down
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