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Improve numerical stability of tanh #54

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2 changes: 1 addition & 1 deletion LICENSE
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
MIT License

Copyright (c) 2025 Robert Eisele
Copyright (c) 2026 Robert Eisele

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
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2 changes: 1 addition & 1 deletion README.md
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Expand Up @@ -369,5 +369,5 @@ npm run test

## Copyright and Licensing

Copyright (c) 2025, [Robert Eisele](https://raw.org/)
Copyright (c) 2026, [Robert Eisele](https://raw.org/)
Licensed under the MIT license.
7 changes: 3 additions & 4 deletions dist/complex.js
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Expand Up @@ -173,7 +173,7 @@ const parse = function (a, b) {
case 'string':

z['im'] = /* void */
z['re'] = 0;
z['re'] = 0;

const tokens = a.replace(/_/g, '')
.match(/\d+\.?\d*e[+-]?\d+|\d+\.?\d*|\.\d+|./g);
Expand Down Expand Up @@ -918,11 +918,10 @@ Complex.prototype = {

const a = 2 * this['re'];
const b = 2 * this['im'];
const d = cosh(a) + Math.cos(b);

return new Complex(
sinh(a) / d,
Math.sin(b) / d);
Math.tanh(a) / (1 + Math.cos(b) / cosh(a)),
Math.tan(b) / (1 + cosh(a) / Math.cos(b)));
},

/**
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44 changes: 22 additions & 22 deletions dist/complex.min.js
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7 changes: 3 additions & 4 deletions dist/complex.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -173,7 +173,7 @@ const parse = function (a, b) {
case 'string':

z['im'] = /* void */
z['re'] = 0;
z['re'] = 0;

const tokens = a.replace(/_/g, '')
.match(/\d+\.?\d*e[+-]?\d+|\d+\.?\d*|\.\d+|./g);
Expand Down Expand Up @@ -918,11 +918,10 @@ Complex.prototype = {

const a = 2 * this['re'];
const b = 2 * this['im'];
const d = cosh(a) + Math.cos(b);

return new Complex(
sinh(a) / d,
Math.sin(b) / d);
Math.tanh(a) / (1 + Math.cos(b) / cosh(a)),
Math.tan(b) / (1 + cosh(a) / Math.cos(b)));
},

/**
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9 changes: 4 additions & 5 deletions src/complex.js
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@@ -1,8 +1,8 @@
/**
* @license Complex.js v2.4.3 11/13/2025
* @license Complex.js v2.4.3 5/21/2026
* https://raw.org/article/complex-numbers-in-javascript/
*
* Copyright (c) 2025, Robert Eisele (https://raw.org/)
* Copyright (c) 2026, Robert Eisele (https://raw.org/)
* Licensed under the MIT license.
**/

Expand Down Expand Up @@ -924,11 +924,10 @@ Complex.prototype = {

const a = 2 * this['re'];
const b = 2 * this['im'];
const d = cosh(a) + Math.cos(b);

return new Complex(
sinh(a) / d,
Math.sin(b) / d);
Math.tanh(a) / (1 + Math.cos(b) / cosh(a)),
Math.tan(b) / (1 + cosh(a) / Math.cos(b)));
},

/**
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13 changes: 12 additions & 1 deletion tests/complex.test.js
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Expand Up @@ -526,7 +526,7 @@ var functionTests = [{
}, {
set: { re: 1, im: 3 },
fn: "tanh",
expect: "0.7680176472869112 - 0.059168539566050726i"
expect: "0.7680176472869112 - 0.05916853956605073i"
}, {
set: { re: 1, im: 3 },
fn: "inverse",
Expand Down Expand Up @@ -1005,6 +1005,17 @@ describe("Complex Details", function () {
assert.strictEqual(Complex({ re: 0.451, im: 0 }).acosh().im, 1.1029108863861707);
});

it('should calculate the tanh correctly', function () {

var a = new Complex(1, 1).tanh();
var b = new Complex(100, 100).tanh();
var c = new Complex(1000, 1000).tanh();

assert.strictEqual(a.toString(), "1.0839233273386946 + 0.27175258531951174i");
assert.strictEqual(b.toString(), "1");
assert.strictEqual(c.toString(), "1");
});

it('should handle sum', function () {
assert.strictEqual(Complex({ abs: 1, arg: 0 }).add({ abs: 1, arg: Math.PI / 2 }).abs(), Math.SQRT2);
assert.strictEqual(Complex({ abs: 1, arg: 0 }).add({ abs: 1, arg: Math.PI / 2 }).arg(), Math.PI / 4);
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