[documentation]: https://docs.rs/cpc
# cpc
calculation + conversion
cpc parses and evaluates strings of math, with support for units and conversion. 128-bit decimal floating points are used for high accuracy.
cpc lets you mix units, so for example `1 km - 1m` results in `Number { value: 999, unit: Meter }`.
[](https://crates.io/crates/cpc)
[](https://docs.rs/cpc)
[List of all supported units](https://docs.rs/cpc/latest/cpc/units/enum.Unit.html)
## CLI Installation
To install the CLI using `cargo`:
```
cargo install cpc
```
To install the CLI directly, grab the appropriate binary from [cpc's Releases page on GitHub](https://github.com/probablykasper/cpc/releases), then place it wherever you normally place binaries on your OS.
## CLI Usage
```
cpc '20c to f'
```
If you installed the binary somewhere that doesn't make binaries global, you would need to specify the path:
```sh
/usr/local/bin/custom/cpc '10+10'
# OR
./cpc '1" in cm'
```
## API Installation
To install the library as a Rust dependency, add cpc to your `Cargo.toml` like so:
```toml
[dependencies]
cpc = "1.*"
```
## API Usage
```rust
use cpc::{eval};
use cpc::units::Unit;
match eval("3m + 1cm", true, Unit::Celsius, false) {
Ok(answer) => {
// answer: Number { value: 301, unit: Unit::Centimeter }
println!("Evaluated value: {} {:?}", answer.value, answer.unit)
},
Err(e) => {
println!("{}", e)
}
}
```
## Examples
```
3 + 4 * 2
8 % 3
(4 + 1)km to light years
10m/2s * 5 trillion s
1 lightyear * 0.001mm in km2
1m/s + 1mi/h in kilometers per h
round(sqrt(2)^4)! liters
10% of abs(sin(pi)) horsepower to watts
```
## Supported unit types
- Normal numbers
- Time
- Length
- Area
- Volume
- Mass
- Digital storage (bytes etc)
- Energy
- Power
- Electric current
- Resistance
- Voltage
- Pressure
- Frequency
- Speed
- Temperature
## Accuracy
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.
## Performance
It's pretty fast and scales well. In my case, `eval()` usually runs under 0.1ms. The biggest performance hit is functions like `log()`. `log(12345)` evaluates in 0.12ms, and `log(e)` in 0.25ms.
To see how fast it is, you can pass the `--debug` flag in CLI, or the `debug` argument to `eval()`.
## Errors
cpc returns `Result`s with basic strings as errors. Just to be safe, you may want to handle panics (You can do that using `std::panic::catch_unwind`).
## Dev Instructions
### Get started
Install [Rust](https://www.rust-lang.org).
Run cpc with a CLI argument as input:
```
cargo run -- '100ms to s'
```
Run with debugging, which shows some extra logs:
```
cargo run -- '100ms to s' --debug
```
Run tests:
```
cargo test
```
Build:
```
cargo build
```
### Adding a unit
Nice resources for adding units:
- https://github.com/ryantenney/gnu-units/blob/master/units.dat
- https://support.google.com/websearch/answer/3284611 (unit list)
- https://translatorscafe.com/unit-converter (unit conversion)
- https://calculateme.com/ (unit conversion)
- https://wikipedia.org/
#### 1. Add the unit
In `src/units.rs`, units are specified like this:
```rs
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 `60`.
I have found [translatorscafe.com](https://www.translatorscafe.com/unit-converter) and [calculateme.com](https://www.calculateme.com/) to be good websites for unit conversion. 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:
```rs
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:
```rs
// ...
match string {
}
// ...
```
### Potential Improvements
#### General
- Support for conversion between Power, Current, Resistance and Voltage. Multiplication and division is currently supported, but not conversions using sqrt or pow.
#### Potential unit types
- Currency: How to go about dynamically updating the weights?
- Fuel consumption
- Data transfer rate
- Color codes
- Force
- Roman numerals
- Angles
- Flow rate
### Cross-compiling
1. [Install Docker](https://docs.docker.com/get-docker/)
2. Install [cross](https://github.com/rust-embedded/cross):
```
cargo install cross
```
3. Build for x86_64 macOS, Linux and Windows:
```sh
cross build --release --target x86_64-apple-darwin && cross build --release --target x86_64-unknown-linux-musl && cross build --release --target x86_64-pc-windows-gnu
```
- Note that building for `x86_64-apple-darwin` only works on macOS
- For more targets, check out [the targets `cross` supports](https://github.com/rust-embedded/cross#supported-targets)
- If you run `cross build` in parallel, you might get a `cargo not found` error
The compiled binaries will now be available inside `target/<target>/release/`. The filename will be either `cpc` or `cpc.exe`.
### Releasing a new version
1. Update `CHANGELOG.md`
2. Bump the version number in `Cargo.toml`
3. Run `cargo test`
4. Cross-compile cpc by following [the steps above](#cross-compiling)
5. Commit and tag in format `v#.#.#`
6. Publish on crates.io:
1. Login by running `cargo login` and following the instructions
2. Test publish to ensure there are no issues
```
cargo publish --dry-run
```
3. Publish
```
cargo publish
```
7. Publish on GitHub
1. Zip the binaries and rename them like `cpc-v1.0.0-macos-x64`
2. Create GitHub release with release notes and attach the zipped binaries