184 lines
4.1 KiB
Markdown
184 lines
4.1 KiB
Markdown
# cpc
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calculation + conversion
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cpc parses and evaluates strings of math, with support for units and conversion. 128-bit decimal floating points are used for high accuracy.
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It also lets you mix units, so for example `1 km - 1m` results in `999 Meter`.
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[](https://crates.io/crates/cpc)
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[](https://docs.rs/cpc)
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[List of all supported units](https://docs.rs/cpc/latest/cpc/units/enum.Unit.html)
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## CLI Installation
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Install using `cargo`:
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```
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cargo install cpc
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```
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To install it manually, grab the appropriate binary from the [GitHub Releases page](https://github.com/probablykasper/cpc/releases) and place it wherever you normally place binaries on your OS.
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## CLI Usage
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```
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cpc '2h/3 to min'
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```
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## Examples
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```
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3 + 4 * 2
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8 % 3
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(4 + 1)km to light years
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10m/2s * 5 trillion s
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1 lightyear * 0.001mm in km2
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1m/s + 1mi/h in kilometers per h
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round(sqrt(2)^4)! liters
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10% of abs(sin(pi)) horsepower to watts
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```
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## Supported unit types
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- Normal numbers
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- Time
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- Length
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- Area
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- Volume
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- Mass
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- Digital storage (bytes etc)
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- Energy
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- Power
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- Electric current
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- Resistance
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- Voltage
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- Pressure
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- Frequency
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- Speed
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- Temperature
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## API Installation
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Add `cpc` as a dependency in `Cargo.toml`.
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## API Usage
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```rust
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use cpc::eval;
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use cpc::units::Unit;
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match eval("3m + 1cm", true, Unit::Celsius, false) {
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Ok(answer) => {
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// answer: Number { value: 301, unit: Unit::Centimeter }
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println!("Evaluated value: {} {:?}", answer.value, answer.unit)
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},
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Err(e) => {
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println!("{e}")
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}
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}
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```
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## Accuracy
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cpc uses 128-bit Decimal Floating Point (d128) numbers instead of Binary Coded Decimals for better accuracy. The result cpc gives will still not always be 100% accurate. I would recommend rounding the result to 20 decimals or less.
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## Dev Instructions
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### Get started
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Install [Rust](https://www.rust-lang.org).
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Run cpc with a CLI argument as input:
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```
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cargo run -- '100ms to s'
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```
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Run in verbose mode, which shows some extra logs:
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```
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cargo run -- '100ms to s' --verbose
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```
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Run tests:
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```
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cargo test
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```
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Build:
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```
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cargo build
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```
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### Adding a unit
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Nice resources for adding units:
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- https://github.com/ryantenney/gnu-units/blob/master/units.dat
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- https://support.google.com/websearch/answer/3284611 (unit list)
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- https://translatorscafe.com/unit-converter (unit conversion)
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- https://calculateme.com (unit conversion)
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- https://wikipedia.org
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#### 1. Add the unit
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In `src/units.rs`, units are specified like this:
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```rs
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pub enum UnitType {
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Time,
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// etc
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}
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// ...
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create_units!(
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Nanosecond: (Time, d128!(1)),
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Microsecond: (Time, d128!(1000)),
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// etc
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)
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```
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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 `60`.
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#### 2. Add a test for the unit
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Make sure to also add a test for each unit. The tests look like this:
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```rs
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assert_eq!(convert_test(1000.0, Meter, Kilometer), 1.0);
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```
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Basically, 1000 Meter == 1 Kilometer.
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#### 3. Add the unit to the lexer
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Text is turned into tokens (some of which are units) in `lexer.rs`. Here's one example:
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```rs
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// ...
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match string {
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"h" | "hr" | "hrs" | "hour" | "hours" => tokens.push(Token::Unit(Hour)),
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// etc
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}
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// ...
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```
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### Potential Improvements
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- Support for conversion between Power, Current, Resistance and Voltage. Multiplication and division is currently supported, but not conversions using sqrt or pow.
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- E notation, like 2E+10
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- Unit types
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- Currency: How to go about dynamically updating the weights?
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- https://api.exchangerate-api.com/v4/latest/USD
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- https://www.coingecko.com/en/api
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- https://developers.coinbase.com/api/v2
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- Timezones
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- Binary/octal/decimal/hexadecimal/base32/base64
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- Fuel consumption
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- Data transfer rate
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- Color codes
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- Force
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- Roman numerals
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- Angles
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- Flow rate
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### Releasing a new version
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1. Update `CHANGELOG.md`
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2. Bump the version number in `Cargo.toml`
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3. Run `cargo test`
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4. Create a git tag in format `v#.#.#`
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5. Add release notes to the generated GitHub release and publish it
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6. Run `cargo publish`
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