CPC/README.md

calculation + conversion

Uses Decimal Floating Point numbers instead of Binary Coded Decimals for better accuracy.

Dev Instructions

Get started

Install Rust. This project was built in Rust 1.40.

Commands

Run cpc with a CLI argument as input:

cargo run -- '100ms to s'

Run tests:

cargo test

Adding a unit

1. Add the unit

In src/units.rs, units are specified like this:

pub enum UnitType {
  Time,
  // etc
}

// ...

create_units!(
  Nanosecond:         (Time, d128!(1)),
  Microsecond:        (Time, d128!(1000)),
  // etc
)

The number associated with a unit is it's "weight". For example, if a second's weight is 1, then a minute's weight is 1000.

I have found translatorscafe.com and calculateme.com to be good websites for unit convertion. Wikipedia is worth looking at as well.

2. Add a test for the unit

Make sure to also add a test for each unit. The tests look like this:

assert_eq!(convert_test(1000.0, Meter, Kilometer), 1.0);

Basically, 1000 Meter == 1 Kilometer.

3. Add the unit to the lexer

Text is turned into tokens (some of which are units) in lexer.rs. Here's one example:

// ...
match string {
  "h" | "hr" | "hrs" | "hour" | "hours" => tokens.push(Token::Unit(Hour)),
  // etc
}
// ...