CLI Unit Convertor

This project moves you from arithmetic execution
to structured transformation systems.

You are no longer applying operators.

You are building:

A conversion engine
A validation layer
A category-based dispatch system
A CLI interaction loop
A floating-point safe output formatter

This is closer to real software than a calculator.

Why This Project Exists

A unit converter forces you to reason about:

Structured mappings (dictionary design)
Dynamic dispatch
Validation logic
String normalization
Floating-point precision
Defensive programming
Extensibility design

You will build a system that converts between:

Length
Mass
Temperature
Time
Speed

Without using external libraries.

System Architecture

Your CLI should follow this structure:

CLI Loop
Command Parsing
Category Validation
Unit Validation
Numeric Parsing
Conversion Engine
Output Formatting
Error Handling

No step should be skipped.

Step 1 - Define the Conversion Model

The correct architecture is:

All units convert to a base unit.

Example (Length):

Base: meters
km → multiply by 1000
cm → multiply by 0.01
mi → multiply by 1609.34

Structure:

CONVERSIONS = {
    "length": {
        "base": "m",
        "units": {
            "m": lambda x: x,
            "km": lambda x: x * 1000,
            "cm": lambda x: x * 0.01,
            "mm": lambda x: x * 0.001,
            "mi": lambda x: x * 1609.34,
        }
    }
}