Compound — Compound Interest Calculator

Compound is a command-line compound interest calculator that helps you plan investments, compare interest rates, build amortization schedules, and project financial growth over time.

All calculation history is stored in ~/.compound/data.jsonl as JSONL records for future reference and comparison.

Prerequisites

• - Python 3.8+ with standard library
• INLINECODE1 shell

Commands

calculate

Calculate compound interest for a given principal, rate, and time period.

Environment Variables:

• - PRINCIPAL (required) — Initial investment amount
• INLINECODE4 (required) — Annual interest rate as percentage (e.g., 5.5)
• INLINECODE5 (required) — Number of years
• INLINECODE6 — Compounding frequency: daily, monthly, quarterly, annually (default: monthly)
• INLINECODE11 — Regular contribution amount (default: 0)
• INLINECODE12 — Contribution frequency: monthly, quarterly, annually (default: monthly)

Example:
CODEBLOCK0

compare

Compare multiple interest rate or compounding frequency scenarios side by side.

Environment Variables:

• - PRINCIPAL (required) — Initial investment amount
• INLINECODE18 (required) — Comma-separated list of rates to compare (e.g., "3,5,7,10")
• INLINECODE19 (required) — Number of years
• INLINECODE20 — Compounding frequency (default: monthly)

schedule

Generate a detailed payment/growth schedule showing balances at each period.

Environment Variables:

• - PRINCIPAL (required) — Initial investment amount
• INLINECODE23 (required) — Annual interest rate as percentage
• INLINECODE24 (required) — Number of years
• INLINECODE25 — Compounding frequency (default: monthly)
• INLINECODE26 — Regular contribution amount (default: 0)

table

Display a year-by-year summary table of investment growth.

Environment Variables:

• - PRINCIPAL (required) — Initial investment amount
• INLINECODE29 (required) — Annual interest rate
• INLINECODE30 (required) — Number of years
• INLINECODE31 — Regular contribution (default: 0)

rate

Calculate the required interest rate to reach a financial goal.

Environment Variables:

• - PRINCIPAL (required) — Starting amount
• INLINECODE34 (required) — Target amount
• INLINECODE35 (required) — Time period in years
• INLINECODE36 — Compounding frequency (default: monthly)

goal

Calculate how long it takes to reach a savings goal.

Environment Variables:

• - PRINCIPAL (required) — Starting amount
• INLINECODE39 (required) — Goal amount
• INLINECODE40 (required) — Annual interest rate
• INLINECODE41 — Regular contribution (default: 0)

chart

Generate an ASCII chart of investment growth over time.

Environment Variables:

• - PRINCIPAL (required) — Initial amount
• INLINECODE44 (required) — Annual interest rate
• INLINECODE45 (required) — Number of years
• INLINECODE46 — Chart width in characters (default: 60)
• INLINECODE47 — Chart height in lines (default: 20)

export

Export calculation history to a file.

Environment Variables:

• - OUTPUT — Output file path (default: stdout)
• INLINECODE50 — Export format: json, csv, jsonl (default: json)
• INLINECODE54 — Specific calculation ID to export (default: all)

config

View or update default configuration settings.

Environment Variables:

• - KEY — Configuration key to set
• INLINECODE57 — Configuration value

history

View past calculations with their results.

Environment Variables:

• - LIMIT — Maximum entries to display (default: 20)
• INLINECODE60 — Sort by: date, principal, rate, total (default: date)

help

Display usage information and available commands.

version

Display the current version of the compound tool.

Data Storage

All calculations are stored in ~/.compound/data.jsonl. Each line is a JSON object with fields:

• - id — Unique calculation identifier
• INLINECODE69 — ISO 8601 creation time
• INLINECODE70 — Calculation type (calculate, compare, goal, etc.)
• INLINECODE71 — Input parameters
• INLINECODE72 — Calculation results (final amount, interest earned, etc.)

Configuration

Config stored in ~/.compound/config.json:

• - default_frequency — Default compounding frequency (default: monthly)
• INLINECODE75 — Currency symbol for display (default: $)
• INLINECODE76 — Number of decimal places (default: 2)

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