feat(core): initial release of financial calculation package with decimal precision

.gitea/workflows/default_nottags.yaml

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+name: "CI Pipeline (nottags)"
+
+on:
+  push:
+    branches:
+      - "**"
+    tags-ignore:
+      - "**"
+
+jobs:
+  security:
+    runs-on: ubuntu-latest
+    continue-on-error: true
+    container:
+      image: code.foss.global/host.today/ht-docker-node:npmci
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up npmci
+        run: npmci node install stable
+
+      - name: Prepare project
+        run: npmci npm prepare
+
+      - name: Audit production dependencies
+        run: npmci command npm audit --audit-level=high --only=prod
+        continue-on-error: true
+
+      - name: Audit development dependencies
+        run: npmci command npm audit --audit-level=high --only=dev
+        continue-on-error: true
+
+  test:
+    needs: security
+    runs-on: ubuntu-latest
+    container:
+      image: code.foss.global/host.today/ht-docker-node:npmci
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up npmci
+        run: npmci node install stable
+
+      - name: Prepare project
+        run: npmci npm prepare
+
+      - name: Install dependencies
+        run: npmci npm install
+
+      - name: Run tests
+        run: npmci npm test
+
+      - name: Build project
+        run: npmci npm build
+
+      - name: Build documentation
+        run: npmci npm buildDocs

.gitea/workflows/default_tags.yaml

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+name: "CI Pipeline (tags)"
+
+on:
+  push:
+    tags:
+      - "*"
+
+env:
+  NPMCI_TOKEN_NPM: ${{ secrets.NPMCI_TOKEN_NPM }}
+  NPMCI_TOKEN_NPM2: ${{ secrets.NPMCI_TOKEN_NPM2 }}
+  NPMCI_GIT_GITHUBTOKEN: ${{ secrets.NPMCI_GIT_GITHUBTOKEN }}
+  NPMCI_URL_CLOUDFLARE: ${{ secrets.NPMCI_URL_CLOUDFLARE }}
+
+jobs:
+  security:
+    runs-on: ubuntu-latest
+    continue-on-error: true
+    container:
+      image: code.foss.global/host.today/ht-docker-node:npmci
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up npmci
+        run: npmci node install stable
+
+      - name: Prepare project
+        run: npmci npm prepare
+
+      - name: Audit production dependencies
+        run: npmci command npm audit --audit-level=high --only=prod
+        continue-on-error: true
+
+      - name: Audit development dependencies
+        run: npmci command npm audit --audit-level=high --only=dev
+        continue-on-error: true
+
+  test:
+    needs: security
+    runs-on: ubuntu-latest
+    container:
+      image: code.foss.global/host.today/ht-docker-node:npmci
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up npmci
+        run: npmci node install stable
+
+      - name: Prepare project
+        run: npmci npm prepare
+
+      - name: Install dependencies
+        run: npmci npm install
+
+      - name: Run tests
+        run: npmci npm test
+
+      - name: Build project
+        run: npmci npm build
+
+      - name: Build documentation
+        run: npmci npm buildDocs
+
+  release:
+    needs: test
+    if: startsWith(github.ref, 'refs/tags/')
+    runs-on: ubuntu-latest
+    container:
+      image: code.foss.global/host.today/ht-docker-node:npmci
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up npmci
+        run: npmci node install stable
+
+      - name: Prepare project
+        run: npmci npm prepare
+
+      - name: Install dependencies
+        run: npmci npm install
+
+      - name: Build project
+        run: npmci npm build
+
+      - name: Publish to npm
+        run: npmci npm publish
+
+  metadata:
+    needs: test
+    if: startsWith(github.ref, 'refs/tags/')
+    runs-on: ubuntu-latest
+    container:
+      image: code.foss.global/host.today/ht-docker-node:npmci
+    continue-on-error: true
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up npmci
+        run: npmci node install stable
+
+      - name: Prepare project
+        run: npmci npm prepare
+
+      - name: Install dependencies
+        run: npmci npm install
+
+      - name: Build project
+        run: npmci npm build
+
+      - name: Generate documentation
+        run: npmci npm buildDocs
+
+      - name: Generate metadata
+        run: npmci command npm pack --dry-run --json
+
+      - name: Trigger further builds
+        run: npmci trigger
+
+      - name: Build and deploy docs
+        run: npmci node install stable && npmci npm prepare && npmci npm install && npmci npm buildDocs

.gitignore

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+# Dependencies
+node_modules/
+
+# Build outputs
+dist_*/
+dist/
+*.tsbuildinfo
+
+# Test outputs
+.nogit/
+
+# IDE
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+
+# Environment
+.env
+.env.local
+.env.*.local
+
+# Coverage
+coverage/
+.nyc_output/
+
+# Temporary files
+tmp/
+temp/

.vscode/settings.json

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+{
+  "typescript.tsdk": "node_modules/typescript/lib",
+  "typescript.enablePromptUseWorkspaceTsdk": true,
+  "editor.formatOnSave": true,
+  "editor.codeActionsOnSave": {
+    "source.fixAll": "explicit"
+  },
+  "files.exclude": {
+    "node_modules": true,
+    "dist_*": true,
+    ".nogit": true
+  }
+}

changelog.md

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+# Changelog
+
+## [1.0.0] - 2025-07-29
+
+### Added
+- Initial release of @fin.cx/calculation
+- Calculator class with high-precision decimal arithmetic
+- Financial class with time value of money calculations (PV, FV, NPV, IRR, XIRR)
+- Interest class with simple, compound, and continuous interest calculations
+- Amortization class with loan schedules and payment analysis
+- Currency class with conversion, formatting, and monetary operations
+- Comprehensive test suite
+- Full TypeScript support
+- CI/CD workflows for automated testing and publishing

license.md

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+MIT License
+
+Copyright (c) 2025 fin.cx
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

npmextra.json

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+{
+  "npmGlobalTools": [],
+  "npmAccessLevel": "public"
+}

package.json

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+{
+  "name": "@fin.cx/calculation",
+  "version": "1.0.0",
+  "private": false,
+  "description": "A unified, cross-platform financial calculation package with decimal precision for accurate financial computations",
+  "main": "dist_ts/index.js",
+  "type": "module",
+  "scripts": {
+    "test": "(tstest test/ --verbose)",
+    "build": "(tsbuild tsfolders --allowimplicitany && tsbundle npm)",
+    "buildDocs": "tsdoc"
+  },
+  "repository": {
+    "type": "git",
+    "url": "code.foss.global/fin.cx/calculation.git"
+  },
+  "keywords": [
+    "financial",
+    "calculation",
+    "finance",
+    "interest",
+    "amortization",
+    "npv",
+    "irr",
+    "decimal",
+    "precision"
+  ],
+  "author": "fin.cx",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/fin-cx/calculation/issues"
+  },
+  "homepage": "https://github.com/fin-cx/calculation#readme",
+  "devDependencies": {
+    "@git.zone/tsbuild": "^2.6.4",
+    "@git.zone/tsbundle": "^2.4.0",
+    "@git.zone/tsrun": "^1.3.3",
+    "@git.zone/tstest": "^2.3.1",
+    "@push.rocks/tapbundle": "^6.0.3",
+    "@types/node": "^22.7.4"
+  },
+  "dependencies": {
+    "@push.rocks/smartpromise": "^4.2.3",
+    "decimal.js": "^10.4.3"
+  },
+  "packageManager": "pnpm@10.11.0"
+}

pnpm-workspace.yaml

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+packages:
+  - '.'

readme.hints.md

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+# Project Hints
+
+## Architecture
+
+This project follows the @push.rocks/smartstate pattern with the following structure:
+- TypeScript source files in `ts/` directory
+- Test files in `test/` directory
+- Built files output to `dist_ts/` directory
+- ES modules configuration (`"type": "module"`)
+
+## Key Design Decisions
+
+1. **Decimal Precision**: Uses decimal.js library to avoid JavaScript floating-point errors
+2. **Class Hierarchy**: Calculator is the base class, other classes extend it for specific domains
+3. **Naming Convention**: Files follow pattern `calculation.classes.*.ts`
+4. **Plugin Pattern**: Dependencies are imported through `calculation.plugins.ts`
+
+## Development Workflow
+
+1. Run tests: `pnpm test`
+2. Build project: `pnpm build`
+3. Type checking: `tsbuild check test/**/* --skiplibcheck`
+4. Testing uses @git.zone/tstest with expect from @push.rocks/tapbundle
+
+## Financial Calculations
+
+- All monetary calculations use decimal arithmetic for accuracy
+- Interest calculations support multiple compounding frequencies
+- Financial functions follow standard financial formulas
+- Currency class handles formatting based on locale conventions
+
+## Testing Strategy
+
+- Cross-platform tests in `test.both.ts`
+- Tests cover accuracy, edge cases, and error handling
+- Precision tests ensure decimal accuracy is maintained

readme.md

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+# @fin.cx/calculation
+
+> Professional financial calculations with decimal precision for JavaScript and TypeScript
+
+[![npm version](https://img.shields.io/npm/v/@fin.cx/calculation.svg)](https://www.npmjs.com/package/@fin.cx/calculation)
+[![TypeScript](https://img.shields.io/badge/TypeScript-Ready-blue.svg)](https://www.typescriptlang.org/)
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+
+## 🎯 Why @fin.cx/calculation?
+
+JavaScript's floating-point arithmetic can lead to precision errors in financial calculations:
+
+```javascript
+// JavaScript floating point problem
+0.1 + 0.2 // 0.30000000000000004 ❌
+
+// With @fin.cx/calculation
+calculator.add(0.1, 0.2) // 0.3 ✅
+```
+
+This package provides **accurate financial calculations** using decimal arithmetic, making it perfect for:
+
+- 🏦 Banking applications
+- 💰 Investment analysis tools
+- 📊 Financial reporting systems
+- 🏢 Accounting software
+- 💳 Payment processing systems
+- 📈 Trading platforms
+
+## ✨ Features
+
+- **🔢 Decimal Precision**: Built on decimal.js for accurate calculations
+- **📐 Comprehensive Functions**: Time value of money, interest calculations, loan amortization, and more
+- **💱 Currency Support**: Built-in currency formatting and conversion
+- **🌍 Cross-Platform**: Works in Node.js and browsers
+- **📘 TypeScript First**: Full type safety and IntelliSense support
+- **🧪 Battle-Tested**: Extensive test suite ensures reliability
+- **🚀 Zero Dependencies**: Only depends on decimal.js for core functionality
+
+## 📦 Installation
+
+```bash
+npm install @fin.cx/calculation
+# or
+yarn add @fin.cx/calculation
+# or
+pnpm add @fin.cx/calculation
+```
+
+## 🚀 Quick Start
+
+```typescript
+import { Calculator, Financial, Currency } from '@fin.cx/calculation';
+
+// Basic calculations with precision
+const calc = new Calculator();
+const result = calc.add(0.1, 0.2); // 0.3 (exact)
+
+// Financial calculations
+const financial = new Financial();
+const payment = financial.payment(200000, 0.045/12, 360); // Monthly mortgage payment
+
+// Currency operations
+const currency = new Currency();
+currency.setExchangeRate('USD', 'EUR', 0.85);
+const euros = currency.convert(100, 'USD', 'EUR'); // Convert $100 to €85
+```
+
+## 📚 Core Classes
+
+### Calculator - Precision Arithmetic
+
+```typescript
+const calc = new Calculator({ precision: 10 });
+
+// Basic operations
+calc.add(10.5, 20.3);           // 30.8
+calc.subtract(100, 45.5);       // 54.5
+calc.multiply(15, 3.5);         // 52.5
+calc.divide(100, 3);            // 33.3333333333...
+
+// Advanced operations
+calc.power(2, 8);               // 256
+calc.sqrt(16);                  // 4
+calc.ln(Math.E);                // 1
+calc.round(3.14159, 2);         // 3.14
+```
+
+### Financial - Time Value of Money
+
+```typescript
+const financial = new Financial();
+
+// Present Value - How much is $10,000 in 5 years worth today at 5% interest?
+const pv = financial.presentValue(10000, 0.05, 5); // $7,835.26
+
+// Future Value - How much will $5,000 be worth in 10 years at 7% interest?
+const fv = financial.futureValue(5000, 0.07, 10); // $9,835.76
+
+// Loan Payment - Monthly payment for $200,000 mortgage at 4.5% for 30 years
+const pmt = financial.payment(200000, 0.045/12, 360); // $1,013.37
+
+// Net Present Value - Is this investment worth it?
+const cashFlows = [-50000, 15000, 15000, 15000, 15000, 20000];
+const npv = financial.npv(0.1, cashFlows); // $7,946.11 (positive = good investment)
+
+// Internal Rate of Return - What's the return rate?
+const irr = financial.irr(cashFlows); // 16.89%
+```
+
+### Interest - Various Interest Calculations
+
+```typescript
+const interest = new Interest();
+
+// Simple Interest - $1,000 at 5% for 2 years
+const simple = interest.simple(1000, 0.05, 2); // $100
+
+// Compound Interest - $1,000 at 5% for 2 years, compounded monthly
+const compound = interest.compound(1000, 0.05, 2, 'monthly'); // $104.94
+
+// Effective Annual Rate - What's the real rate with monthly compounding?
+const ear = interest.effectiveAnnualRate(0.12, 'monthly'); // 12.68%
+
+// Rule of 72 - How long to double your money at 8%?
+const years = interest.ruleOf72(8); // ~9 years
+```
+
+### Amortization - Loan Schedules
+
+```typescript
+const amortization = new Amortization();
+
+// Generate complete loan schedule
+const schedule = amortization.schedule({
+  principal: 250000,
+  annualRate: 0.045,
+  termYears: 30,
+  extraPayment: 200 // Optional extra monthly payment
+});
+
+// Analyze the schedule
+console.log(`Monthly Payment: $${schedule.monthlyPayment.toFixed(2)}`);
+console.log(`Total Interest: $${schedule.totalInterest.toFixed(2)}`);
+console.log(`Payoff in ${schedule.payments.length} months`);
+
+// Each payment includes:
+schedule.payments[0]; // {
+//   period: 1,
+//   payment: 1266.71,
+//   principal: 329.21,
+//   interest: 937.50,
+//   balance: 249670.79,
+//   cumulativePrincipal: 329.21,
+//   cumulativeInterest: 937.50
+// }
+```
+
+### Currency - Money Formatting & Conversion
+
+```typescript
+const currency = new Currency();
+
+// Set exchange rates
+currency.setExchangeRates([
+  { from: 'USD', to: 'EUR', rate: 0.85 },
+  { from: 'USD', to: 'GBP', rate: 0.73 },
+  { from: 'USD', to: 'JPY', rate: 110 }
+]);
+
+// Convert currencies
+const euros = currency.convert(1000, 'USD', 'EUR'); // €850
+
+// Format currency for display
+currency.format(1234.56, 'USD'); // "$1,234.56"
+currency.format(1234.56, 'EUR'); // "€1.234,56"
+currency.format(1234.56, 'JPY'); // "¥1,235"
+
+// Money operations (ensures same currency)
+const total = currency.addMoney(
+  currency.money(100, 'USD'),
+  currency.money(50, 'USD')
+); // $150
+
+// Percentage calculations
+currency.percentage(200, 15);           // 30 (15% of 200)
+currency.discount(100, 20);             // 80 (20% off)
+currency.withTax(100, 0.08);           // 108 (8% tax)
+```
+
+## Precision and Accuracy
+
+All calculations use decimal.js internally to avoid floating-point precision errors common in JavaScript:
+
+```typescript
+// JavaScript floating point error
+console.log(0.1 + 0.2); // 0.30000000000000004
+
+// @fin.cx/calculation precision
+const calc = new Calculator();
+const result = calc.add(0.1, 0.2);
+console.log(calc.toString(result)); // "0.3"
+```
+
+## API Reference
+
+### Calculator Options
+
+```typescript
+interface ICalculatorOptions {
+  precision?: number;    // Decimal places (default: 10)
+  rounding?: number;     // Rounding mode (default: ROUND_HALF_UP)
+}
+```
+
+### Compounding Frequencies
+
+- `'annually'` - Once per year
+- `'semiannually'` - Twice per year
+- `'quarterly'` - Four times per year
+- `'monthly'` - Twelve times per year
+- `'weekly'` - 52 times per year
+- `'daily'` - 365 times per year
+- `'continuous'` - Continuous compounding
+
+### Currency Options
+
+```typescript
+interface ICurrencyOptions {
+  code: string;
+  symbol?: string;
+  decimals?: number;
+  thousandsSeparator?: string;
+  decimalSeparator?: string;
+  symbolPosition?: 'before' | 'after';
+  spaceBetweenSymbolAndValue?: boolean;
+}
+```
+
+## 🏗️ Real-World Examples
+
+### Mortgage Calculator
+
+```typescript
+import { Financial, Amortization } from '@fin.cx/calculation';
+
+function calculateMortgage(homePrice: number, downPayment: number, rate: number, years: number) {
+  const financial = new Financial();
+  const amortization = new Amortization();
+  
+  const loanAmount = homePrice - downPayment;
+  const monthlyRate = rate / 12;
+  const months = years * 12;
+  
+  const monthlyPayment = financial.payment(loanAmount, monthlyRate, months);
+  const totalPaid = monthlyPayment.mul(months);
+  const totalInterest = totalPaid.sub(loanAmount);
+  
+  const schedule = amortization.schedule({
+    principal: loanAmount,
+    annualRate: rate,
+    termYears: years
+  });
+  
+  return {
+    monthlyPayment,
+    totalInterest,
+    schedule
+  };
+}
+```
+
+### Investment Analysis
+
+```typescript
+import { Financial } from '@fin.cx/calculation';
+
+function analyzeInvestment(initialInvestment: number, cashFlows: number[], discountRate: number) {
+  const financial = new Financial();
+  
+  // Add initial investment as negative cash flow
+  const allCashFlows = [-initialInvestment, ...cashFlows];
+  
+  const npv = financial.npv(discountRate, allCashFlows);
+  const irr = financial.irr(allCashFlows);
+  const paybackPeriod = calculatePaybackPeriod(allCashFlows);
+  
+  return {
+    npv: npv.toFixed(2),
+    irr: (irr.mul(100)).toFixed(2) + '%',
+    profitable: npv.greaterThan(0),
+    paybackPeriod
+  };
+}
+```
+
+### Multi-Currency Invoice System
+
+```typescript
+import { Currency } from '@fin.cx/calculation';
+
+class InvoiceSystem {
+  private currency = new Currency();
+  
+  constructor() {
+    // Set up exchange rates (in production, fetch from API)
+    this.currency.setExchangeRates([
+      { from: 'USD', to: 'EUR', rate: 0.85 },
+      { from: 'USD', to: 'GBP', rate: 0.73 }
+    ]);
+  }
+  
+  calculateInvoice(items: Array<{price: number, quantity: number}>, currency: string, taxRate: number) {
+    const subtotal = items.reduce((sum, item) => 
+      this.currency.add(sum, this.currency.multiply(item.price, item.quantity)), 
+      0
+    );
+    
+    const tax = this.currency.tax(subtotal, taxRate);
+    const total = this.currency.add(subtotal, tax);
+    
+    return {
+      subtotal: this.currency.format(subtotal, currency),
+      tax: this.currency.format(tax, currency),
+      total: this.currency.format(total, currency),
+      // Provide total in other currencies
+      totalUSD: this.currency.format(this.currency.convert(total, currency, 'USD'), 'USD'),
+      totalEUR: this.currency.format(this.currency.convert(total, currency, 'EUR'), 'EUR')
+    };
+  }
+}
+```
+
+## 🔧 Configuration
+
+### Calculator Precision
+
+```typescript
+// Default precision is 10 decimal places
+const calc = new Calculator();
+
+// Custom precision for specific use cases
+const highPrecision = new Calculator({ precision: 20 });
+const moneyCalc = new Calculator({ precision: 4, rounding: Decimal.ROUND_HALF_UP });
+```
+
+### Custom Currencies
+
+```typescript
+const currency = new Currency();
+
+// Register a custom currency
+currency.registerCurrency({
+  code: 'BTC',
+  symbol: '₿',
+  decimals: 8,
+  thousandsSeparator: ',',
+  decimalSeparator: '.',
+  symbolPosition: 'before'
+});
+
+// Use it like any other currency
+currency.format(0.00042, 'BTC'); // "₿0.00042000"
+```
+
+## 🧪 Testing
+
+The package includes comprehensive tests for all calculations:
+
+```bash
+# Run tests
+npm test
+
+# Run tests with coverage
+npm run test:coverage
+```
+
+## 🤝 Contributing
+
+Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.
+
+1. Fork the repository
+2. Create your feature branch (`git checkout -b feature/AmazingFeature`)
+3. Commit your changes (`git commit -m 'Add some AmazingFeature'`)
+4. Push to the branch (`git push origin feature/AmazingFeature`)
+5. Open a Pull Request
+
+## 📄 License
+
+This project is licensed under the MIT License - see the [LICENSE](license.md) file for details.
+
+## 🙏 Acknowledgments
+
+- Built on top of [decimal.js](https://github.com/MikeMcl/decimal.js/) for decimal arithmetic
+- Inspired by financial calculation needs in modern web applications
+- Thanks to all contributors who have helped shape this library
+
+## 📞 Support
+
+- 📧 Email: support@fin.cx
+- 🐛 Issues: [GitHub Issues](https://github.com/fin-cx/calculation/issues)
+- 💬 Discussions: [GitHub Discussions](https://github.com/fin-cx/calculation/discussions)
+
+---
+
+Made with ❤️ by the fin.cx team

test/test.both.ts

@@ -0,0 +1,246 @@
+import { expect, tap } from '@git.zone/tstest/tapbundle';
+import * as calculation from '../ts/index.js';
+
+tap.test('Calculator class should perform basic arithmetic with decimal precision', async () => {
+  const calc = new calculation.Calculator({ precision: 10 });
+  
+  // Test addition
+  const sum = calc.add(0.1, 0.2);
+  expect(calc.toString(sum)).toEqual('0.3');
+  
+  // Test subtraction
+  const diff = calc.subtract(1, 0.9);
+  expect(calc.toString(diff)).toEqual('0.1');
+  
+  // Test multiplication
+  const product = calc.multiply(0.1, 0.2);
+  expect(calc.toString(product)).toEqual('0.02');
+  
+  // Test division
+  const quotient = calc.divide(1, 3);
+  expect(calc.toString(quotient)).toEqual('0.3333333333');
+  
+  // Test power
+  const power = calc.power(2, 3);
+  expect(calc.toNumber(power)).toEqual(8);
+  
+  // Test square root
+  const sqrt = calc.sqrt(9);
+  expect(calc.toNumber(sqrt)).toEqual(3);
+  
+  // Test rounding
+  const rounded = calc.round(3.14159, 2);
+  expect(calc.toString(rounded)).toEqual('3.14');
+});
+
+tap.test('Financial class should calculate time value of money correctly', async () => {
+  const financial = new calculation.Financial();
+  
+  // Test Present Value
+  const pv = financial.presentValue(1000, 0.05, 5);
+  expect(financial.round(pv, 2).toString()).toEqual('783.53');
+  
+  // Test Future Value
+  const fv = financial.futureValue(1000, 0.05, 5);
+  expect(financial.round(fv, 2).toString()).toEqual('1276.28');
+  
+  // Test Payment
+  const pmt = financial.payment(10000, 0.05/12, 60);
+  expect(financial.round(pmt, 2).toString()).toEqual('188.71');
+  
+  // Test NPV
+  const cashFlows = [-1000, 300, 300, 300, 300, 300];
+  const npv = financial.npv(0.1, cashFlows);
+  expect(financial.round(npv, 2).toString()).toEqual('137.24');
+  
+  // Test periods calculation
+  const periods = financial.periods(1000, 2000, 0.08);
+  expect(financial.round(periods, 2).toString()).toEqual('9.01');
+  
+  // Test rate calculation
+  const rate = financial.rate(1000, 2000, 10);
+  expect(financial.round(rate, 4).toString()).toEqual('0.0718');
+});
+
+tap.test('Financial class should calculate IRR correctly', async () => {
+  const financial = new calculation.Financial();
+  
+  // Test basic IRR
+  const cashFlows = [-1000, 200, 300, 400, 500];
+  const irr = financial.irr(cashFlows);
+  expect(financial.round(irr, 4).toString()).toEqual('0.1283');
+  
+  // Test MIRR
+  const mirr = financial.mirr(cashFlows, 0.1, 0.12);
+  expect(financial.round(mirr, 4).toString()).toEqual('0.1256');
+});
+
+tap.test('Interest class should calculate different types of interest', async () => {
+  const interest = new calculation.Interest();
+  
+  // Test simple interest
+  const simple = interest.simple(1000, 0.05, 2);
+  expect(interest.toString(simple)).toEqual('100');
+  
+  // Test simple interest amount
+  const simpleAmount = interest.simpleAmount(1000, 0.05, 2);
+  expect(interest.toString(simpleAmount)).toEqual('1100');
+  
+  // Test compound interest annually
+  const compound = interest.compound(1000, 0.05, 2, 'annually');
+  expect(interest.round(compound, 2).toString()).toEqual('102.5');
+  
+  // Test compound interest monthly
+  const compoundMonthly = interest.compound(1000, 0.12, 1, 'monthly');
+  expect(interest.round(compoundMonthly, 2).toString()).toEqual('126.83');
+  
+  // Test continuous compound interest
+  const continuous = interest.compound(1000, 0.05, 2, 'continuous');
+  expect(interest.round(continuous, 2).toString()).toEqual('105.17');
+  
+  // Test effective annual rate
+  const ear = interest.effectiveAnnualRate(0.12, 'monthly');
+  expect(interest.round(ear, 4).toString()).toEqual('0.1268');
+  
+  // Test real rate
+  const realRate = interest.realRate(0.08, 0.03);
+  expect(interest.round(realRate, 4).toString()).toEqual('0.0485');
+  
+  // Test Rule of 72
+  const rule72 = interest.ruleOf72(8);
+  expect(interest.toString(rule72)).toEqual('9');
+});
+
+tap.test('Amortization class should generate correct loan schedules', async () => {
+  const amortization = new calculation.Amortization();
+  
+  // Test basic loan schedule
+  const schedule = amortization.schedule({
+    principal: 10000,
+    annualRate: 0.05,
+    termYears: 2
+  });
+  
+  expect(schedule.payments).toHaveLength(24);
+  expect(amortization.round(schedule.monthlyPayment, 2).toString()).toEqual('438.71');
+  expect(amortization.round(schedule.totalInterest, 2).toString()).toEqual('529.13');
+  
+  // Test remaining balance
+  const balance = amortization.remainingBalance(10000, 0.05, 24, 12);
+  expect(amortization.round(balance, 2).toString()).toEqual('5124.71');
+  
+  // Test max loan amount
+  const maxLoan = amortization.maxLoanAmount(1000, 0.05, 360);
+  expect(amortization.round(maxLoan, 2).toString()).toEqual('186281.62');
+  
+  // Test LTV ratio
+  const ltv = amortization.ltv(80000, 100000);
+  expect(amortization.toString(ltv)).toEqual('0.8');
+  
+  // Test DTI ratio
+  const dti = amortization.dti(1500, 5000);
+  expect(amortization.toString(dti)).toEqual('0.3');
+});
+
+tap.test('Currency class should handle currency operations correctly', async () => {
+  const currency = new calculation.Currency();
+  
+  // Set up exchange rates
+  currency.setExchangeRate('USD', 'EUR', 0.85);
+  currency.setExchangeRate('USD', 'GBP', 0.73);
+  
+  // Test currency conversion
+  const converted = currency.convert(100, 'USD', 'EUR');
+  expect(currency.toString(converted)).toEqual('85');
+  
+  // Test inverse conversion
+  const inverse = currency.convert(85, 'EUR', 'USD');
+  expect(currency.round(inverse, 2).toString()).toEqual('100');
+  
+  // Test currency formatting
+  const formatted = currency.format(1234.56, 'USD');
+  expect(formatted).toEqual('$1,234.56');
+  
+  const formattedEur = currency.format(1234.56, 'EUR');
+  expect(formattedEur).toEqual('€1.234,56');
+  
+  const formattedJpy = currency.format(1234.56, 'JPY');
+  expect(formattedJpy).toEqual('¥1,235');
+  
+  // Test parsing
+  const parsed = currency.parse('$1,234.56', 'USD');
+  expect(currency.toString(parsed)).toEqual('1234.56');
+  
+  // Test money operations
+  const money1 = currency.money(100, 'USD');
+  const money2 = currency.money(50, 'USD');
+  const sum = currency.addMoney(money1, money2);
+  expect(currency.toString(sum.amount)).toEqual('150');
+  
+  // Test percentage calculations
+  const percentage = currency.percentage(100, 15);
+  expect(currency.toString(percentage)).toEqual('15');
+  
+  // Test tax calculations
+  const withTax = currency.withTax(100, 0.08);
+  expect(currency.toString(withTax)).toEqual('108');
+  
+  const extracted = currency.extractTax(108, 0.08);
+  expect(currency.round(extracted.baseAmount, 2).toString()).toEqual('100');
+  expect(currency.round(extracted.taxAmount, 2).toString()).toEqual('8');
+});
+
+tap.test('Edge cases and error handling', async () => {
+  const calc = new calculation.Calculator();
+  const financial = new calculation.Financial();
+  const interest = new calculation.Interest();
+  const amortization = new calculation.Amortization();
+  const currency = new calculation.Currency();
+  
+  // Test division by zero
+  expect(() => calc.divide(10, 0)).toThrow();
+  
+  // Test zero interest rate in periods calculation
+  expect(() => financial.periods(1000, 2000, 0)).toThrow();
+  
+  // Test zero periods in rate calculation
+  expect(() => financial.rate(1000, 2000, 0)).toThrow();
+  
+  // Test doubling time with zero rate
+  expect(() => interest.doubleTime(0)).toThrow();
+  
+  // Test Rule of 72 with zero rate
+  expect(() => interest.ruleOf72(0)).toThrow();
+  
+  // Test LTV with zero property value
+  expect(() => amortization.ltv(100000, 0)).toThrow();
+  
+  // Test DTI with zero income
+  expect(() => amortization.dti(1000, 0)).toThrow();
+  
+  // Test currency conversion without exchange rate
+  expect(() => currency.convert(100, 'USD', 'JPY')).toThrow();
+  
+  // Test adding money with different currencies
+  const usdMoney = currency.money(100, 'USD');
+  const eurMoney = currency.money(100, 'EUR');
+  expect(() => currency.addMoney(usdMoney, eurMoney)).toThrow();
+});
+
+tap.test('Precision and accuracy tests', async () => {
+  const calc = new calculation.Calculator({ precision: 20 });
+  
+  // Test high precision calculation
+  const result = calc.divide(1, 3);
+  expect(calc.toString(result)).toEqual('0.33333333333333333333');
+  
+  // Test very small numbers
+  const small = calc.multiply('0.000000001', '0.000000001');
+  expect(calc.toString(small)).toEqual('1e-18');
+  
+  // Test very large numbers
+  const large = calc.multiply('1000000000000', '1000000000000');
+  expect(calc.toString(large)).toEqual('1e+24');
+});
+
+tap.start();

ts/00_commitinfo_data.ts

@@ -0,0 +1,8 @@
+/**
+ * autocreated commitinfo by @push.rocks/commitinfo
+ */
+export const commitinfo = {
+  name: '@fin.cx/calculation',
+  version: '1.0.0',
+  description: 'A unified, cross-platform financial calculation package with decimal precision for accurate financial computations'
+};

ts/calculation.classes.amortization.ts

@@ -0,0 +1,313 @@
+import * as plugins from './calculation.plugins.js';
+import { Calculator } from './calculation.classes.calculator.js';
+
+export interface IAmortizationPayment {
+  period: number;
+  payment: plugins.Decimal;
+  principal: plugins.Decimal;
+  interest: plugins.Decimal;
+  balance: plugins.Decimal;
+  cumulativePrincipal: plugins.Decimal;
+  cumulativeInterest: plugins.Decimal;
+}
+
+export interface IAmortizationSchedule {
+  payments: IAmortizationPayment[];
+  totalPayment: plugins.Decimal;
+  totalPrincipal: plugins.Decimal;
+  totalInterest: plugins.Decimal;
+  monthlyPayment: plugins.Decimal;
+}
+
+export interface ILoanOptions {
+  principal: plugins.Decimal.Value;
+  annualRate: plugins.Decimal.Value;
+  termYears?: plugins.Decimal.Value;
+  termMonths?: plugins.Decimal.Value;
+  paymentFrequency?: 'monthly' | 'biweekly' | 'weekly';
+  extraPayment?: plugins.Decimal.Value;
+}
+
+/**
+ * Amortization calculations class for loan schedules and payment analysis
+ */
+export class Amortization extends Calculator {
+  constructor() {
+    super({ precision: 15 });
+  }
+
+  /**
+   * Generate a complete amortization schedule
+   * @param options Loan options
+   */
+  public schedule(options: ILoanOptions): IAmortizationSchedule {
+    const principal = this.decimal(options.principal);
+    const annualRate = this.decimal(options.annualRate);
+    const termMonths = this.calculateTermMonths(options);
+    const extraPayment = options.extraPayment ? this.decimal(options.extraPayment) : this.decimal(0);
+    
+    const monthlyRate = this.divide(annualRate, 12);
+    const monthlyPayment = this.calculatePayment(principal, monthlyRate, termMonths);
+    
+    const payments: IAmortizationPayment[] = [];
+    let balance = principal;
+    let cumulativePrincipal = this.decimal(0);
+    let cumulativeInterest = this.decimal(0);
+    
+    for (let period = 1; period <= termMonths.toNumber() && balance.greaterThan(0); period++) {
+      const interestPayment = this.multiply(balance, monthlyRate);
+      const scheduledPrincipal = this.subtract(monthlyPayment, interestPayment);
+      
+      // Apply extra payment to principal
+      const totalPrincipal = this.add(scheduledPrincipal, extraPayment);
+      
+      // Ensure we don't pay more than the remaining balance
+      const actualPrincipal = this.min(totalPrincipal, balance);
+      const actualPayment = this.add(interestPayment, actualPrincipal);
+      
+      balance = this.subtract(balance, actualPrincipal);
+      cumulativePrincipal = this.add(cumulativePrincipal, actualPrincipal);
+      cumulativeInterest = this.add(cumulativeInterest, interestPayment);
+      
+      payments.push({
+        period,
+        payment: actualPayment,
+        principal: actualPrincipal,
+        interest: interestPayment,
+        balance: balance,
+        cumulativePrincipal: cumulativePrincipal,
+        cumulativeInterest: cumulativeInterest
+      });
+      
+      // If balance is paid off early, stop
+      if (balance.isZero()) {
+        break;
+      }
+    }
+    
+    const totalPayment = payments.reduce((sum, p) => this.add(sum, p.payment), this.decimal(0));
+    const totalPrincipal = cumulativePrincipal;
+    const totalInterest = cumulativeInterest;
+    
+    return {
+      payments,
+      totalPayment,
+      totalPrincipal,
+      totalInterest,
+      monthlyPayment
+    };
+  }
+
+  /**
+   * Calculate monthly payment for a loan
+   */
+  private calculatePayment(
+    principal: plugins.Decimal,
+    monthlyRate: plugins.Decimal,
+    termMonths: plugins.Decimal
+  ): plugins.Decimal {
+    if (monthlyRate.isZero()) {
+      return this.divide(principal, termMonths);
+    }
+    
+    const numerator = this.multiply(principal, monthlyRate);
+    const denominator = this.subtract(
+      1,
+      this.power(this.add(1, monthlyRate), this.multiply(-1, termMonths))
+    );
+    
+    return this.divide(numerator, denominator);
+  }
+
+  /**
+   * Calculate total term in months
+   */
+  private calculateTermMonths(options: ILoanOptions): plugins.Decimal {
+    if (options.termMonths) {
+      return this.decimal(options.termMonths);
+    } else if (options.termYears) {
+      return this.multiply(this.decimal(options.termYears), 12);
+    } else {
+      throw new Error('Either termYears or termMonths must be specified');
+    }
+  }
+
+  /**
+   * Calculate remaining balance after a specific number of payments
+   * @param principal Original loan amount
+   * @param annualRate Annual interest rate
+   * @param termMonths Total term in months
+   * @param paymentsMade Number of payments made
+   */
+  public remainingBalance(
+    principal: plugins.Decimal.Value,
+    annualRate: plugins.Decimal.Value,
+    termMonths: plugins.Decimal.Value,
+    paymentsMade: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const p = this.decimal(principal);
+    const r = this.divide(this.decimal(annualRate), 12);
+    const n = this.decimal(termMonths);
+    const m = this.decimal(paymentsMade);
+    
+    if (r.isZero()) {
+      const paymentAmount = this.divide(p, n);
+      const paidAmount = this.multiply(paymentAmount, m);
+      return this.subtract(p, paidAmount);
+    }
+    
+    const onePlusR = this.add(1, r);
+    const factor1 = this.power(onePlusR, n);
+    const factor2 = this.power(onePlusR, m);
+    
+    const numerator = this.multiply(p, this.subtract(factor1, factor2));
+    const denominator = this.subtract(factor1, 1);
+    
+    return this.divide(numerator, denominator);
+  }
+
+  /**
+   * Calculate interest paid over a specific period
+   * @param schedule The amortization schedule
+   * @param startPeriod Start period (inclusive)
+   * @param endPeriod End period (inclusive)
+   */
+  public interestForPeriod(
+    schedule: IAmortizationSchedule,
+    startPeriod: number,
+    endPeriod: number
+  ): plugins.Decimal {
+    return schedule.payments
+      .filter(p => p.period >= startPeriod && p.period <= endPeriod)
+      .reduce((sum, p) => this.add(sum, p.interest), this.decimal(0));
+  }
+
+  /**
+   * Calculate principal paid over a specific period
+   * @param schedule The amortization schedule
+   * @param startPeriod Start period (inclusive)
+   * @param endPeriod End period (inclusive)
+   */
+  public principalForPeriod(
+    schedule: IAmortizationSchedule,
+    startPeriod: number,
+    endPeriod: number
+  ): plugins.Decimal {
+    return schedule.payments
+      .filter(p => p.period >= startPeriod && p.period <= endPeriod)
+      .reduce((sum, p) => this.add(sum, p.principal), this.decimal(0));
+  }
+
+  /**
+   * Calculate the payoff date with extra payments
+   * @param options Loan options with extra payment
+   */
+  public payoffDate(options: ILoanOptions, startDate: Date = new Date()): Date {
+    const schedule = this.schedule(options);
+    const lastPayment = schedule.payments[schedule.payments.length - 1];
+    
+    const monthsToPayoff = lastPayment.period;
+    const payoffDate = new Date(startDate);
+    payoffDate.setMonth(payoffDate.getMonth() + monthsToPayoff);
+    
+    return payoffDate;
+  }
+
+  /**
+   * Calculate interest savings with extra payments
+   * @param regularOptions Loan options without extra payment
+   * @param extraPaymentOptions Loan options with extra payment
+   */
+  public interestSavings(
+    regularOptions: ILoanOptions,
+    extraPaymentOptions: ILoanOptions
+  ): plugins.Decimal {
+    const regularSchedule = this.schedule(regularOptions);
+    const extraSchedule = this.schedule(extraPaymentOptions);
+    
+    return this.subtract(regularSchedule.totalInterest, extraSchedule.totalInterest);
+  }
+
+  /**
+   * Calculate biweekly payment amount (26 payments per year)
+   * @param monthlyPayment The regular monthly payment
+   */
+  public biweeklyPayment(monthlyPayment: plugins.Decimal.Value): plugins.Decimal {
+    return this.divide(this.decimal(monthlyPayment), 2);
+  }
+
+  /**
+   * Calculate weekly payment amount (52 payments per year)
+   * @param monthlyPayment The regular monthly payment
+   */
+  public weeklyPayment(monthlyPayment: plugins.Decimal.Value): plugins.Decimal {
+    const monthly = this.decimal(monthlyPayment);
+    const yearlyPayment = this.multiply(monthly, 12);
+    return this.divide(yearlyPayment, 52);
+  }
+
+  /**
+   * Calculate the maximum loan amount based on payment capacity
+   * @param maxPayment Maximum monthly payment
+   * @param annualRate Annual interest rate
+   * @param termMonths Term in months
+   */
+  public maxLoanAmount(
+    maxPayment: plugins.Decimal.Value,
+    annualRate: plugins.Decimal.Value,
+    termMonths: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const payment = this.decimal(maxPayment);
+    const r = this.divide(this.decimal(annualRate), 12);
+    const n = this.decimal(termMonths);
+    
+    if (r.isZero()) {
+      return this.multiply(payment, n);
+    }
+    
+    const onePlusR = this.add(1, r);
+    const factor = this.power(onePlusR, this.multiply(-1, n));
+    const numerator = this.subtract(1, factor);
+    const denominator = this.divide(numerator, r);
+    
+    return this.multiply(payment, denominator);
+  }
+
+  /**
+   * Calculate loan-to-value ratio (LTV)
+   * @param loanAmount The loan amount
+   * @param propertyValue The property value
+   */
+  public ltv(
+    loanAmount: plugins.Decimal.Value,
+    propertyValue: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const loan = this.decimal(loanAmount);
+    const value = this.decimal(propertyValue);
+    
+    if (value.isZero()) {
+      throw new Error('Property value cannot be zero');
+    }
+    
+    return this.divide(loan, value);
+  }
+
+  /**
+   * Calculate debt-to-income ratio (DTI)
+   * @param monthlyDebtPayments Total monthly debt payments
+   * @param monthlyIncome Monthly gross income
+   */
+  public dti(
+    monthlyDebtPayments: plugins.Decimal.Value,
+    monthlyIncome: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const debt = this.decimal(monthlyDebtPayments);
+    const income = this.decimal(monthlyIncome);
+    
+    if (income.isZero()) {
+      throw new Error('Monthly income cannot be zero');
+    }
+    
+    return this.divide(debt, income);
+  }
+}

ts/calculation.classes.calculator.ts

@@ -0,0 +1,178 @@
+import * as plugins from './calculation.plugins.js';
+
+export interface ICalculatorOptions {
+  precision?: number;
+  rounding?: plugins.Decimal.Rounding;
+}
+
+/**
+ * Base calculator class providing high-precision decimal arithmetic
+ * for financial calculations
+ */
+export class Calculator {
+  private precision: number;
+  private rounding: plugins.Decimal.Rounding;
+
+  constructor(options: ICalculatorOptions = {}) {
+    this.precision = options.precision || 10;
+    this.rounding = options.rounding || plugins.Decimal.ROUND_HALF_UP;
+    
+    // Configure Decimal.js globally for this calculator instance
+    plugins.Decimal.set({
+      precision: this.precision,
+      rounding: this.rounding
+    });
+  }
+
+  /**
+   * Create a Decimal instance from a value
+   */
+  public decimal(value: plugins.Decimal.Value): plugins.Decimal {
+    return new plugins.Decimal(value);
+  }
+
+  /**
+   * Add two or more numbers with decimal precision
+   */
+  public add(...values: plugins.Decimal.Value[]): plugins.Decimal {
+    return values.reduce<plugins.Decimal>((sum, value) => {
+      return sum.add(this.decimal(value));
+    }, new plugins.Decimal(0));
+  }
+
+  /**
+   * Subtract numbers with decimal precision
+   */
+  public subtract(minuend: plugins.Decimal.Value, ...subtrahends: plugins.Decimal.Value[]): plugins.Decimal {
+    let result = new plugins.Decimal(minuend);
+    for (const subtrahend of subtrahends) {
+      result = result.sub(subtrahend);
+    }
+    return result;
+  }
+
+  /**
+   * Multiply numbers with decimal precision
+   */
+  public multiply(...values: plugins.Decimal.Value[]): plugins.Decimal {
+    return values.reduce<plugins.Decimal>((product, value) => {
+      return product.mul(this.decimal(value));
+    }, new plugins.Decimal(1));
+  }
+
+  /**
+   * Divide numbers with decimal precision
+   */
+  public divide(dividend: plugins.Decimal.Value, divisor: plugins.Decimal.Value): plugins.Decimal {
+    const divisorDecimal = new plugins.Decimal(divisor);
+    if (divisorDecimal.isZero()) {
+      throw new Error('Division by zero');
+    }
+    return new plugins.Decimal(dividend).div(divisor);
+  }
+
+  /**
+   * Calculate power with decimal precision
+   */
+  public power(base: plugins.Decimal.Value, exponent: plugins.Decimal.Value): plugins.Decimal {
+    return new plugins.Decimal(base).pow(exponent);
+  }
+
+  /**
+   * Calculate square root with decimal precision
+   */
+  public sqrt(value: plugins.Decimal.Value): plugins.Decimal {
+    return new plugins.Decimal(value).sqrt();
+  }
+
+  /**
+   * Calculate natural logarithm with decimal precision
+   */
+  public ln(value: plugins.Decimal.Value): plugins.Decimal {
+    return new plugins.Decimal(value).ln();
+  }
+
+  /**
+   * Calculate logarithm base 10 with decimal precision
+   */
+  public log10(value: plugins.Decimal.Value): plugins.Decimal {
+    return new plugins.Decimal(value).log();
+  }
+
+  /**
+   * Calculate exponential (e^x) with decimal precision
+   */
+  public exp(value: plugins.Decimal.Value): plugins.Decimal {
+    return new plugins.Decimal(value).exp();
+  }
+
+  /**
+   * Round a number to specified decimal places
+   */
+  public round(value: plugins.Decimal.Value, decimalPlaces: number = 0): plugins.Decimal {
+    return new plugins.Decimal(value).toDecimalPlaces(decimalPlaces);
+  }
+
+  /**
+   * Check if a value equals another value
+   */
+  public equals(value1: plugins.Decimal.Value, value2: plugins.Decimal.Value): boolean {
+    return new plugins.Decimal(value1).equals(value2);
+  }
+
+  /**
+   * Check if a value is greater than another value
+   */
+  public greaterThan(value1: plugins.Decimal.Value, value2: plugins.Decimal.Value): boolean {
+    return new plugins.Decimal(value1).greaterThan(value2);
+  }
+
+  /**
+   * Check if a value is less than another value
+   */
+  public lessThan(value1: plugins.Decimal.Value, value2: plugins.Decimal.Value): boolean {
+    return new plugins.Decimal(value1).lessThan(value2);
+  }
+
+  /**
+   * Get the minimum value from an array of values
+   */
+  public min(...values: plugins.Decimal.Value[]): plugins.Decimal {
+    return plugins.Decimal.min(...values);
+  }
+
+  /**
+   * Get the maximum value from an array of values
+   */
+  public max(...values: plugins.Decimal.Value[]): plugins.Decimal {
+    return plugins.Decimal.max(...values);
+  }
+
+  /**
+   * Calculate the absolute value
+   */
+  public abs(value: plugins.Decimal.Value): plugins.Decimal {
+    return new plugins.Decimal(value).abs();
+  }
+
+  /**
+   * Convert a decimal to a regular number
+   */
+  public toNumber(value: plugins.Decimal.Value): number {
+    return new plugins.Decimal(value).toNumber();
+  }
+
+  /**
+   * Convert a decimal to a string
+   */
+  public toString(value: plugins.Decimal.Value): string {
+    return new plugins.Decimal(value).toString();
+  }
+
+  /**
+   * Convert a decimal to a fixed-point string
+   */
+  public toFixed(value: plugins.Decimal.Value, decimalPlaces: number = 2): string {
+    return new plugins.Decimal(value).toFixed(decimalPlaces);
+  }
+}

ts/calculation.classes.currency.ts

@@ -0,0 +1,328 @@
+import * as plugins from './calculation.plugins.js';
+import { Calculator } from './calculation.classes.calculator.js';
+
+export interface ICurrencyOptions {
+  code: string;
+  symbol?: string;
+  decimals?: number;
+  thousandsSeparator?: string;
+  decimalSeparator?: string;
+  symbolPosition?: 'before' | 'after';
+  spaceBetweenSymbolAndValue?: boolean;
+}
+
+export interface IExchangeRate {
+  from: string;
+  to: string;
+  rate: plugins.Decimal.Value;
+  timestamp?: Date;
+}
+
+export interface IMoneyValue {
+  amount: plugins.Decimal;
+  currency: string;
+}
+
+/**
+ * Currency calculations and formatting class
+ */
+export class Currency extends Calculator {
+  private currencies: Map<string, ICurrencyOptions> = new Map();
+  private exchangeRates: Map<string, plugins.Decimal> = new Map();
+
+  constructor() {
+    super({ precision: 10 });
+    this.initializeCommonCurrencies();
+  }
+
+  /**
+   * Initialize common currencies with their default options
+   */
+  private initializeCommonCurrencies(): void {
+    const commonCurrencies: ICurrencyOptions[] = [
+      { code: 'USD', symbol: '$', decimals: 2, thousandsSeparator: ',', decimalSeparator: '.', symbolPosition: 'before' },
+      { code: 'EUR', symbol: '€', decimals: 2, thousandsSeparator: '.', decimalSeparator: ',', symbolPosition: 'before' },
+      { code: 'GBP', symbol: '£', decimals: 2, thousandsSeparator: ',', decimalSeparator: '.', symbolPosition: 'before' },
+      { code: 'JPY', symbol: '¥', decimals: 0, thousandsSeparator: ',', decimalSeparator: '.', symbolPosition: 'before' },
+      { code: 'CHF', symbol: 'Fr.', decimals: 2, thousandsSeparator: "'", decimalSeparator: '.', symbolPosition: 'after', spaceBetweenSymbolAndValue: true },
+      { code: 'CAD', symbol: 'C$', decimals: 2, thousandsSeparator: ',', decimalSeparator: '.', symbolPosition: 'before' },
+      { code: 'AUD', symbol: 'A$', decimals: 2, thousandsSeparator: ',', decimalSeparator: '.', symbolPosition: 'before' },
+      { code: 'CNY', symbol: '¥', decimals: 2, thousandsSeparator: ',', decimalSeparator: '.', symbolPosition: 'before' },
+      { code: 'INR', symbol: '₹', decimals: 2, thousandsSeparator: ',', decimalSeparator: '.', symbolPosition: 'before' },
+      { code: 'BTC', symbol: '₿', decimals: 8, thousandsSeparator: ',', decimalSeparator: '.', symbolPosition: 'before' }
+    ];
+
+    commonCurrencies.forEach(currency => {
+      this.currencies.set(currency.code, currency);
+    });
+  }
+
+  /**
+   * Register a new currency or update existing one
+   */
+  public registerCurrency(options: ICurrencyOptions): void {
+    this.currencies.set(options.code, {
+      ...options,
+      decimals: options.decimals ?? 2,
+      thousandsSeparator: options.thousandsSeparator ?? ',',
+      decimalSeparator: options.decimalSeparator ?? '.',
+      symbolPosition: options.symbolPosition ?? 'before',
+      spaceBetweenSymbolAndValue: options.spaceBetweenSymbolAndValue ?? false
+    });
+  }
+
+  /**
+   * Set exchange rate between two currencies
+   * @param from Source currency code
+   * @param to Target currency code
+   * @param rate Exchange rate (how many 'to' units per 'from' unit)
+   */
+  public setExchangeRate(from: string, to: string, rate: plugins.Decimal.Value): void {
+    const key = `${from}_${to}`;
+    this.exchangeRates.set(key, this.decimal(rate));
+    
+    // Also set the inverse rate
+    const inverseKey = `${to}_${from}`;
+    const inverseRate = this.divide(1, rate);
+    this.exchangeRates.set(inverseKey, inverseRate);
+  }
+
+  /**
+   * Set multiple exchange rates at once
+   */
+  public setExchangeRates(rates: IExchangeRate[]): void {
+    rates.forEach(rate => {
+      this.setExchangeRate(rate.from, rate.to, rate.rate);
+    });
+  }
+
+  /**
+   * Convert amount from one currency to another
+   * @param amount The amount to convert
+   * @param from Source currency code
+   * @param to Target currency code
+   */
+  public convert(
+    amount: plugins.Decimal.Value,
+    from: string,
+    to: string
+  ): plugins.Decimal {
+    if (from === to) {
+      return this.decimal(amount);
+    }
+
+    const key = `${from}_${to}`;
+    const rate = this.exchangeRates.get(key);
+
+    if (!rate) {
+      throw new Error(`Exchange rate not found for ${from} to ${to}`);
+    }
+
+    return this.multiply(amount, rate);
+  }
+
+  /**
+   * Create a money value object
+   */
+  public money(amount: plugins.Decimal.Value, currency: string): IMoneyValue {
+    return {
+      amount: this.decimal(amount),
+      currency
+    };
+  }
+
+  /**
+   * Add two money values (must be same currency)
+   */
+  public addMoney(money1: IMoneyValue, money2: IMoneyValue): IMoneyValue {
+    if (money1.currency !== money2.currency) {
+      throw new Error('Cannot add money values with different currencies');
+    }
+
+    return {
+      amount: this.add(money1.amount, money2.amount),
+      currency: money1.currency
+    };
+  }
+
+  /**
+   * Subtract two money values (must be same currency)
+   */
+  public subtractMoney(money1: IMoneyValue, money2: IMoneyValue): IMoneyValue {
+    if (money1.currency !== money2.currency) {
+      throw new Error('Cannot subtract money values with different currencies');
+    }
+
+    return {
+      amount: this.subtract(money1.amount, money2.amount),
+      currency: money1.currency
+    };
+  }
+
+  /**
+   * Format currency value for display
+   * @param amount The amount to format
+   * @param currencyCode The currency code
+   * @param options Override formatting options
+   */
+  public format(
+    amount: plugins.Decimal.Value,
+    currencyCode: string,
+    options?: Partial<ICurrencyOptions>
+  ): string {
+    const currency = this.currencies.get(currencyCode);
+    
+    if (!currency) {
+      throw new Error(`Currency ${currencyCode} not registered`);
+    }
+
+    const formatOptions = { ...currency, ...options };
+    const value = this.decimal(amount);
+    
+    // Round to the correct number of decimal places
+    const rounded = this.round(value, formatOptions.decimals || 0);
+    
+    // Convert to string with fixed decimals
+    let numberStr = this.toFixed(rounded, formatOptions.decimals || 0);
+    
+    // Split into integer and decimal parts
+    const parts = numberStr.split('.');
+    
+    // Apply thousands separator to integer part
+    if (formatOptions.thousandsSeparator) {
+      parts[0] = parts[0].replace(/\B(?=(\d{3})+(?!\d))/g, formatOptions.thousandsSeparator);
+    }
+    
+    // Join parts with appropriate decimal separator
+    if (parts.length === 2) {
+      numberStr = parts.join(formatOptions.decimalSeparator || '.');
+    } else {
+      numberStr = parts[0];
+    }
+    
+    // Add currency symbol
+    if (formatOptions.symbol) {
+      const space = formatOptions.spaceBetweenSymbolAndValue ? ' ' : '';
+      
+      if (formatOptions.symbolPosition === 'after') {
+        return `${numberStr}${space}${formatOptions.symbol}`;
+      } else {
+        return `${formatOptions.symbol}${space}${numberStr}`;
+      }
+    }
+    
+    return numberStr;
+  }
+
+  /**
+   * Parse a formatted currency string back to a decimal value
+   * @param formattedValue The formatted string
+   * @param currencyCode The currency code
+   */
+  public parse(formattedValue: string, currencyCode: string): plugins.Decimal {
+    const currency = this.currencies.get(currencyCode);
+    
+    if (!currency) {
+      throw new Error(`Currency ${currencyCode} not registered`);
+    }
+    
+    // Remove currency symbol
+    let cleanValue = formattedValue;
+    if (currency.symbol) {
+      cleanValue = cleanValue.replace(currency.symbol, '');
+    }
+    
+    // Remove thousands separator
+    if (currency.thousandsSeparator) {
+      cleanValue = cleanValue.replace(new RegExp(`\\${currency.thousandsSeparator}`, 'g'), '');
+    }
+    
+    // Replace decimal separator with standard dot
+    if (currency.decimalSeparator && currency.decimalSeparator !== '.') {
+      cleanValue = cleanValue.replace(currency.decimalSeparator, '.');
+    }
+    
+    // Remove any remaining spaces and parse
+    cleanValue = cleanValue.trim();
+    
+    return this.decimal(cleanValue);
+  }
+
+  /**
+   * Round amount to currency's standard decimal places
+   */
+  public roundToCurrency(amount: plugins.Decimal.Value, currencyCode: string): plugins.Decimal {
+    const currency = this.currencies.get(currencyCode);
+    
+    if (!currency) {
+      throw new Error(`Currency ${currencyCode} not registered`);
+    }
+    
+    return this.round(amount, currency.decimals || 0);
+  }
+
+  /**
+   * Calculate percentage of amount
+   * @param amount The base amount
+   * @param percentage The percentage (e.g., 15 for 15%)
+   */
+  public percentage(amount: plugins.Decimal.Value, percentage: plugins.Decimal.Value): plugins.Decimal {
+    const percent = this.divide(percentage, 100);
+    return this.multiply(amount, percent);
+  }
+
+  /**
+   * Calculate markup amount
+   * @param cost The base cost
+   * @param markupPercentage The markup percentage
+   */
+  public markup(cost: plugins.Decimal.Value, markupPercentage: plugins.Decimal.Value): plugins.Decimal {
+    const markupAmount = this.percentage(cost, markupPercentage);
+    return this.add(cost, markupAmount);
+  }
+
+  /**
+   * Calculate discount amount
+   * @param price The original price
+   * @param discountPercentage The discount percentage
+   */
+  public discount(price: plugins.Decimal.Value, discountPercentage: plugins.Decimal.Value): plugins.Decimal {
+    const discountAmount = this.percentage(price, discountPercentage);
+    return this.subtract(price, discountAmount);
+  }
+
+  /**
+   * Calculate tax amount
+   * @param amount The base amount
+   * @param taxRate The tax rate (e.g., 0.08 for 8%)
+   */
+  public tax(amount: plugins.Decimal.Value, taxRate: plugins.Decimal.Value): plugins.Decimal {
+    return this.multiply(amount, taxRate);
+  }
+
+  /**
+   * Calculate total with tax
+   * @param amount The base amount
+   * @param taxRate The tax rate
+   */
+  public withTax(amount: plugins.Decimal.Value, taxRate: plugins.Decimal.Value): plugins.Decimal {
+    const taxAmount = this.tax(amount, taxRate);
+    return this.add(amount, taxAmount);
+  }
+
+  /**
+   * Extract base amount from a tax-inclusive price
+   * @param totalAmount The total amount including tax
+   * @param taxRate The tax rate
+   */
+  public extractTax(totalAmount: plugins.Decimal.Value, taxRate: plugins.Decimal.Value): {
+    baseAmount: plugins.Decimal;
+    taxAmount: plugins.Decimal;
+  } {
+    const divisor = this.add(1, taxRate);
+    const baseAmount = this.divide(totalAmount, divisor);
+    const taxAmount = this.subtract(totalAmount, baseAmount);
+    
+    return { baseAmount, taxAmount };
+  }
+}

ts/calculation.classes.financial.ts

@@ -0,0 +1,325 @@
+import * as plugins from './calculation.plugins.js';
+import { Calculator } from './calculation.classes.calculator.js';
+
+export interface ICashFlow {
+  amount: plugins.Decimal.Value;
+  period?: number;
+}
+
+/**
+ * Financial calculations class providing time value of money and investment analysis functions
+ */
+export class Financial extends Calculator {
+  constructor() {
+    super({ precision: 15 });
+  }
+
+  /**
+   * Calculate Present Value (PV)
+   * @param futureValue The future value
+   * @param rate The interest rate per period
+   * @param periods The number of periods
+   */
+  public presentValue(
+    futureValue: plugins.Decimal.Value, 
+    rate: plugins.Decimal.Value, 
+    periods: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const r = this.decimal(rate);
+    const n = this.decimal(periods);
+    const fv = this.decimal(futureValue);
+    
+    const denominator = this.power(this.add(1, r), n);
+    return this.divide(fv, denominator);
+  }
+
+  /**
+   * Calculate Future Value (FV)
+   * @param presentValue The present value
+   * @param rate The interest rate per period
+   * @param periods The number of periods
+   */
+  public futureValue(
+    presentValue: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    periods: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const r = this.decimal(rate);
+    const n = this.decimal(periods);
+    const pv = this.decimal(presentValue);
+    
+    const multiplier = this.power(this.add(1, r), n);
+    return this.multiply(pv, multiplier);
+  }
+
+  /**
+   * Calculate Payment (PMT) for a loan
+   * @param principal The loan principal
+   * @param rate The interest rate per period
+   * @param periods The number of periods
+   */
+  public payment(
+    principal: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    periods: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const r = this.decimal(rate);
+    const n = this.decimal(periods);
+    const p = this.decimal(principal);
+    
+    if (r.isZero()) {
+      return this.divide(p, n);
+    }
+    
+    const numerator = this.multiply(p, r);
+    const denominator = this.subtract(1, this.power(this.add(1, r), this.multiply(-1, n)));
+    
+    return this.divide(numerator, denominator);
+  }
+
+  /**
+   * Calculate Net Present Value (NPV)
+   * @param rate The discount rate
+   * @param cashFlows Array of cash flows (first element is initial investment, usually negative)
+   */
+  public npv(rate: plugins.Decimal.Value, cashFlows: plugins.Decimal.Value[]): plugins.Decimal {
+    const r = this.decimal(rate);
+    
+    return cashFlows.reduce<plugins.Decimal>((npv, cashFlow, period) => {
+      const cf = this.decimal(cashFlow);
+      const discountFactor = this.power(this.add(1, r), period);
+      const presentValue = this.divide(cf, discountFactor);
+      return this.add(npv, presentValue);
+    }, this.decimal(0));
+  }
+
+  /**
+   * Calculate Internal Rate of Return (IRR) using Newton-Raphson method
+   * @param cashFlows Array of cash flows
+   * @param guess Initial guess for IRR (default: 0.1)
+   * @param tolerance Convergence tolerance (default: 0.000001)
+   * @param maxIterations Maximum iterations (default: 1000)
+   */
+  public irr(
+    cashFlows: plugins.Decimal.Value[],
+    guess: plugins.Decimal.Value = 0.1,
+    tolerance: plugins.Decimal.Value = 0.000001,
+    maxIterations: number = 1000
+  ): plugins.Decimal {
+    let rate = this.decimal(guess);
+    const tol = this.decimal(tolerance);
+    
+    for (let i = 0; i < maxIterations; i++) {
+      const npvValue = this.npv(rate, cashFlows);
+      const npvDerivative = this.npvDerivative(rate, cashFlows);
+      
+      if (npvDerivative.isZero()) {
+        throw new Error('IRR calculation failed: derivative is zero');
+      }
+      
+      const newRate = this.subtract(rate, this.divide(npvValue, npvDerivative));
+      
+      if (this.abs(this.subtract(newRate, rate)).lessThan(tol)) {
+        return newRate;
+      }
+      
+      rate = newRate;
+    }
+    
+    throw new Error('IRR calculation failed: maximum iterations reached');
+  }
+
+  /**
+   * Calculate the derivative of NPV with respect to rate (for IRR calculation)
+   */
+  private npvDerivative(rate: plugins.Decimal.Value, cashFlows: plugins.Decimal.Value[]): plugins.Decimal {
+    const r = this.decimal(rate);
+    
+    return cashFlows.reduce<plugins.Decimal>((derivative, cashFlow, period) => {
+      if (period === 0) return derivative;
+      
+      const cf = this.decimal(cashFlow);
+      const negPeriod = this.decimal(period).neg();
+      const onePlusR = this.add(1, r);
+      const power = this.add(negPeriod, -1);
+      const discountFactor = this.power(onePlusR, power);
+      const termDerivative = this.multiply(this.multiply(negPeriod, cf), discountFactor);
+      
+      return this.add(derivative, termDerivative);
+    }, this.decimal(0));
+  }
+
+  /**
+   * Calculate Modified Internal Rate of Return (MIRR)
+   * @param cashFlows Array of cash flows
+   * @param financeRate Rate for negative cash flows
+   * @param reinvestRate Rate for positive cash flows
+   */
+  public mirr(
+    cashFlows: plugins.Decimal.Value[],
+    financeRate: plugins.Decimal.Value,
+    reinvestRate: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const fRate = this.decimal(financeRate);
+    const rRate = this.decimal(reinvestRate);
+    const n = cashFlows.length - 1;
+    
+    let pvNegative = this.decimal(0);
+    let fvPositive = this.decimal(0);
+    
+    cashFlows.forEach((cashFlow, period) => {
+      const cf = this.decimal(cashFlow);
+      if (cf.lessThan(0)) {
+        pvNegative = this.add(pvNegative, this.presentValue(cf, fRate, period));
+      } else {
+        fvPositive = this.add(fvPositive, this.futureValue(cf, rRate, n - period));
+      }
+    });
+    
+    if (pvNegative.isZero() || fvPositive.isZero()) {
+      throw new Error('MIRR calculation failed: no negative or positive cash flows');
+    }
+    
+    const ratio = this.divide(fvPositive, this.abs(pvNegative));
+    const result = this.subtract(this.power(ratio, this.divide(1, n)), 1);
+    
+    return result;
+  }
+
+  /**
+   * Calculate the number of periods for an investment to reach a target value
+   * @param presentValue The present value
+   * @param futureValue The future value
+   * @param rate The interest rate per period
+   */
+  public periods(
+    presentValue: plugins.Decimal.Value,
+    futureValue: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const pv = this.decimal(presentValue);
+    const fv = this.decimal(futureValue);
+    const r = this.decimal(rate);
+    
+    if (r.isZero()) {
+      throw new Error('Cannot calculate periods with zero interest rate');
+    }
+    
+    const ratio = this.divide(fv, pv);
+    const numerator = this.ln(ratio);
+    const denominator = this.ln(this.add(1, r));
+    
+    return this.divide(numerator, denominator);
+  }
+
+  /**
+   * Calculate the interest rate given PV, FV, and periods
+   * @param presentValue The present value
+   * @param futureValue The future value
+   * @param periods The number of periods
+   */
+  public rate(
+    presentValue: plugins.Decimal.Value,
+    futureValue: plugins.Decimal.Value,
+    periods: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const pv = this.decimal(presentValue);
+    const fv = this.decimal(futureValue);
+    const n = this.decimal(periods);
+    
+    if (n.isZero()) {
+      throw new Error('Cannot calculate rate with zero periods');
+    }
+    
+    const ratio = this.divide(fv, pv);
+    const exponent = this.divide(1, n);
+    const result = this.subtract(this.power(ratio, exponent), 1);
+    
+    return result;
+  }
+
+  /**
+   * Calculate Extended Internal Rate of Return (XIRR) for irregular cash flows
+   * @param cashFlows Array of cash flow objects with amounts and dates
+   * @param dates Array of dates corresponding to cash flows
+   * @param guess Initial guess for XIRR (default: 0.1)
+   */
+  public xirr(
+    cashFlows: plugins.Decimal.Value[],
+    dates: Date[],
+    guess: plugins.Decimal.Value = 0.1
+  ): plugins.Decimal {
+    if (cashFlows.length !== dates.length) {
+      throw new Error('Cash flows and dates arrays must have the same length');
+    }
+    
+    const startDate = dates[0];
+    const yearFractions = dates.map(date => {
+      const daysDiff = (date.getTime() - startDate.getTime()) / (1000 * 60 * 60 * 24);
+      return this.divide(daysDiff, 365);
+    });
+    
+    let rate = this.decimal(guess);
+    const tolerance = this.decimal(0.000001);
+    const maxIterations = 1000;
+    
+    for (let i = 0; i < maxIterations; i++) {
+      const xnpv = this.xnpv(rate, cashFlows, yearFractions);
+      const xnpvDerivative = this.xnpvDerivative(rate, cashFlows, yearFractions);
+      
+      if (xnpvDerivative.isZero()) {
+        throw new Error('XIRR calculation failed: derivative is zero');
+      }
+      
+      const newRate = this.subtract(rate, this.divide(xnpv, xnpvDerivative));
+      
+      if (this.abs(this.subtract(newRate, rate)).lessThan(tolerance)) {
+        return newRate;
+      }
+      
+      rate = newRate;
+    }
+    
+    throw new Error('XIRR calculation failed: maximum iterations reached');
+  }
+
+  /**
+   * Calculate XNPV for irregular cash flows
+   */
+  private xnpv(
+    rate: plugins.Decimal.Value,
+    cashFlows: plugins.Decimal.Value[],
+    yearFractions: plugins.Decimal[]
+  ): plugins.Decimal {
+    const r = this.decimal(rate);
+    
+    return cashFlows.reduce<plugins.Decimal>((npv, cashFlow, index) => {
+      const cf = this.decimal(cashFlow);
+      const t = yearFractions[index];
+      const discountFactor = this.power(this.add(1, r), t);
+      const presentValue = this.divide(cf, discountFactor);
+      return this.add(npv, presentValue);
+    }, this.decimal(0));
+  }
+
+  /**
+   * Calculate the derivative of XNPV
+   */
+  private xnpvDerivative(
+    rate: plugins.Decimal.Value,
+    cashFlows: plugins.Decimal.Value[],
+    yearFractions: plugins.Decimal[]
+  ): plugins.Decimal {
+    const r = this.decimal(rate);
+    
+    return cashFlows.reduce<plugins.Decimal>((derivative, cashFlow, index) => {
+      const cf = this.decimal(cashFlow);
+      const t = yearFractions[index];
+      const negT = this.multiply(-1, t);
+      const discountFactor = this.power(this.add(1, r), this.subtract(negT, 1));
+      const termDerivative = this.multiply(this.multiply(negT, cf), discountFactor);
+      
+      return this.add(derivative, termDerivative);
+    }, this.decimal(0));
+  }
+}

ts/calculation.classes.interest.ts

@@ -0,0 +1,297 @@
+import * as plugins from './calculation.plugins.js';
+import { Calculator } from './calculation.classes.calculator.js';
+
+export type CompoundingFrequency = 'annually' | 'semiannually' | 'quarterly' | 'monthly' | 'weekly' | 'daily' | 'continuous';
+
+export interface IInterestOptions {
+  principal: plugins.Decimal.Value;
+  rate: plugins.Decimal.Value;
+  time: plugins.Decimal.Value;
+  compoundingFrequency?: CompoundingFrequency;
+}
+
+/**
+ * Interest calculations class providing various interest computation methods
+ */
+export class Interest extends Calculator {
+  private readonly frequencyMap: Record<CompoundingFrequency, number> = {
+    annually: 1,
+    semiannually: 2,
+    quarterly: 4,
+    monthly: 12,
+    weekly: 52,
+    daily: 365,
+    continuous: 0
+  };
+
+  constructor() {
+    super({ precision: 15 });
+  }
+
+  /**
+   * Calculate simple interest
+   * @param principal The principal amount
+   * @param rate The annual interest rate (as decimal, e.g., 0.05 for 5%)
+   * @param time The time period in years
+   */
+  public simple(
+    principal: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    time: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const p = this.decimal(principal);
+    const r = this.decimal(rate);
+    const t = this.decimal(time);
+    
+    return this.multiply(p, r, t);
+  }
+
+  /**
+   * Calculate simple interest amount (principal + interest)
+   */
+  public simpleAmount(
+    principal: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    time: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const p = this.decimal(principal);
+    const interest = this.simple(principal, rate, time);
+    
+    return this.add(p, interest);
+  }
+
+  /**
+   * Calculate compound interest
+   * @param principal The principal amount
+   * @param rate The annual interest rate (as decimal)
+   * @param time The time period in years
+   * @param frequency The compounding frequency (default: annually)
+   */
+  public compound(
+    principal: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    time: plugins.Decimal.Value,
+    frequency: CompoundingFrequency = 'annually'
+  ): plugins.Decimal {
+    const p = this.decimal(principal);
+    const r = this.decimal(rate);
+    const t = this.decimal(time);
+    
+    if (frequency === 'continuous') {
+      return this.continuousCompound(principal, rate, time);
+    }
+    
+    const n = this.decimal(this.frequencyMap[frequency]);
+    const amount = this.compoundAmount(principal, rate, time, frequency);
+    
+    return this.subtract(amount, p);
+  }
+
+  /**
+   * Calculate compound interest amount (principal + interest)
+   */
+  public compoundAmount(
+    principal: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    time: plugins.Decimal.Value,
+    frequency: CompoundingFrequency = 'annually'
+  ): plugins.Decimal {
+    const p = this.decimal(principal);
+    const r = this.decimal(rate);
+    const t = this.decimal(time);
+    
+    if (frequency === 'continuous') {
+      return this.continuousCompoundAmount(principal, rate, time);
+    }
+    
+    const n = this.decimal(this.frequencyMap[frequency]);
+    const ratePerPeriod = this.divide(r, n);
+    const periods = this.multiply(n, t);
+    const multiplier = this.power(this.add(1, ratePerPeriod), periods);
+    
+    return this.multiply(p, multiplier);
+  }
+
+  /**
+   * Calculate continuous compound interest
+   */
+  private continuousCompound(
+    principal: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    time: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const p = this.decimal(principal);
+    const amount = this.continuousCompoundAmount(principal, rate, time);
+    
+    return this.subtract(amount, p);
+  }
+
+  /**
+   * Calculate continuous compound interest amount
+   */
+  private continuousCompoundAmount(
+    principal: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    time: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const p = this.decimal(principal);
+    const r = this.decimal(rate);
+    const t = this.decimal(time);
+    
+    const exponent = this.multiply(r, t);
+    const multiplier = this.exp(exponent);
+    
+    return this.multiply(p, multiplier);
+  }
+
+  /**
+   * Calculate effective annual rate (EAR) from nominal rate
+   * @param nominalRate The nominal annual interest rate
+   * @param frequency The compounding frequency
+   */
+  public effectiveAnnualRate(
+    nominalRate: plugins.Decimal.Value,
+    frequency: CompoundingFrequency = 'annually'
+  ): plugins.Decimal {
+    const r = this.decimal(nominalRate);
+    
+    if (frequency === 'continuous') {
+      return this.subtract(this.exp(r), 1);
+    }
+    
+    const n = this.decimal(this.frequencyMap[frequency]);
+    const ratePerPeriod = this.divide(r, n);
+    const onePlusRate = this.add(1, ratePerPeriod);
+    const compounded = this.power(onePlusRate, n);
+    
+    return this.subtract(compounded, 1);
+  }
+
+  /**
+   * Calculate nominal rate from effective annual rate
+   * @param effectiveRate The effective annual rate
+   * @param frequency The compounding frequency
+   */
+  public nominalRate(
+    effectiveRate: plugins.Decimal.Value,
+    frequency: CompoundingFrequency = 'annually'
+  ): plugins.Decimal {
+    const ear = this.decimal(effectiveRate);
+    
+    if (frequency === 'continuous') {
+      return this.ln(this.add(1, ear));
+    }
+    
+    const n = this.decimal(this.frequencyMap[frequency]);
+    const onePlusEar = this.add(1, ear);
+    const exponent = this.divide(1, n);
+    const nthRoot = this.power(onePlusEar, exponent);
+    const ratePerPeriod = this.subtract(nthRoot, 1);
+    
+    return this.multiply(ratePerPeriod, n);
+  }
+
+  /**
+   * Calculate the real interest rate adjusted for inflation
+   * @param nominalRate The nominal interest rate
+   * @param inflationRate The inflation rate
+   */
+  public realRate(
+    nominalRate: plugins.Decimal.Value,
+    inflationRate: plugins.Decimal.Value
+  ): plugins.Decimal {
+    const r = this.decimal(nominalRate);
+    const i = this.decimal(inflationRate);
+    
+    const numerator = this.subtract(r, i);
+    const denominator = this.add(1, i);
+    
+    return this.divide(numerator, denominator);
+  }
+
+  /**
+   * Calculate the time required to double an investment
+   * @param rate The interest rate
+   * @param frequency The compounding frequency
+   */
+  public doubleTime(
+    rate: plugins.Decimal.Value,
+    frequency: CompoundingFrequency = 'annually'
+  ): plugins.Decimal {
+    const r = this.decimal(rate);
+    
+    if (r.isZero()) {
+      throw new Error('Cannot calculate doubling time with zero interest rate');
+    }
+    
+    if (frequency === 'continuous') {
+      return this.divide(this.ln(2), r);
+    }
+    
+    const n = this.decimal(this.frequencyMap[frequency]);
+    const ratePerPeriod = this.divide(r, n);
+    const numerator = this.ln(2);
+    const denominator = this.multiply(n, this.ln(this.add(1, ratePerPeriod)));
+    
+    return this.divide(numerator, denominator);
+  }
+
+  /**
+   * Calculate the Rule of 72 approximation for doubling time
+   * @param rate The annual interest rate (as percentage, e.g., 5 for 5%)
+   */
+  public ruleOf72(rate: plugins.Decimal.Value): plugins.Decimal {
+    const r = this.decimal(rate);
+    
+    if (r.isZero()) {
+      throw new Error('Cannot calculate Rule of 72 with zero interest rate');
+    }
+    
+    return this.divide(72, r);
+  }
+
+  /**
+   * Calculate periodic interest rate from annual rate
+   * @param annualRate The annual interest rate
+   * @param frequency The compounding frequency
+   */
+  public periodicRate(
+    annualRate: plugins.Decimal.Value,
+    frequency: CompoundingFrequency
+  ): plugins.Decimal {
+    if (frequency === 'continuous') {
+      throw new Error('Periodic rate not applicable for continuous compounding');
+    }
+    
+    const r = this.decimal(annualRate);
+    const n = this.decimal(this.frequencyMap[frequency]);
+    
+    return this.divide(r, n);
+  }
+
+  /**
+   * Calculate annual percentage yield (APY)
+   * Same as effective annual rate but commonly used in banking
+   */
+  public apy(
+    nominalRate: plugins.Decimal.Value,
+    frequency: CompoundingFrequency = 'annually'
+  ): plugins.Decimal {
+    return this.effectiveAnnualRate(nominalRate, frequency);
+  }
+
+  /**
+   * Calculate interest on interest (compound interest minus simple interest)
+   */
+  public interestOnInterest(
+    principal: plugins.Decimal.Value,
+    rate: plugins.Decimal.Value,
+    time: plugins.Decimal.Value,
+    frequency: CompoundingFrequency = 'annually'
+  ): plugins.Decimal {
+    const simpleInt = this.simple(principal, rate, time);
+    const compoundInt = this.compound(principal, rate, time, frequency);
+    
+    return this.subtract(compoundInt, simpleInt);
+  }
+}

ts/calculation.plugins.ts

@@ -0,0 +1,7 @@
+import * as smartpromise from '@push.rocks/smartpromise';
+import { Decimal } from 'decimal.js';
+
+export {
+  smartpromise,
+  Decimal
+};

ts/index.ts

@@ -0,0 +1,5 @@
+export * from './calculation.classes.calculator.js';
+export * from './calculation.classes.financial.js';
+export * from './calculation.classes.interest.js';
+export * from './calculation.classes.amortization.js';
+export * from './calculation.classes.currency.js';

tsconfig.json

@@ -0,0 +1,14 @@
+{
+  "compilerOptions": {
+    "experimentalDecorators": true,
+    "useDefineForClassFields": false,
+    "target": "ES2022",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "esModuleInterop": true,
+    "verbatimModuleSyntax": true
+  },
+  "exclude": [
+    "dist_*/**/*.d.ts"
+  ]
+}