daisy/README.md

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A pretty, general-purpose scientific calculator with support for units, derivatives, and more.

Many features are missing, this is still under development.

**Web demo: [here](https://daisy.betalupi.com) (won't work on mobile)**

# 📦 Installation
 - **From source:** `cargo build --release`, binary will be at `./target/release/daisy`
 - **Cargo:** `cargo install daisycalc`
 - **Arch:** `yay -S daisy`
 - **Debian:** coming soon
 - **Nix:** Use `default.nix`. Daisy isn't in nixpkgs yet, you'll need to add something like the following to `configuration.nix`:

```nix
let
  daisy = builtins.fetchGit {
    url = "https://github.com/rm-dr/daisy.git";
    ref = "master";
  } + /default.nix;
in
{
  environment.systemPackages = with pkgs; [
    (callPackage daisy { })
  ];
}
```

# 📹 Screenshot

![Screenshot](https://github.com/rm-dr/daisy/assets/96270320/cc71887a-0fde-46b2-a13b-96b05098b158)

# 🛠️ Features
 - Open-source
 - Carefully designed and easy-to-read prompt
 - Supports many physical units, with metric and binary prefixes
 - Supports exponential notation
 - Clear syntax, parsed input is always re-printed as a sanity check.
 - Useful, detailed error messages


# 📑 Usage

All documentation is built into the prompt. Use the `help` command to view it.

## Evaluate expressions:
 - Basic math: ``103 / 2 * 43``
 - Functions: ``sqrt(1.4^3 + 4) * sin(pi / 4)``
 - Scientific notation: ``1.2e12 * 1e-5``

## Physical units
 - Unit operations: ``2 day + 1 hour``
 - Unit conversion: ``2 day + 1 hour to minutes``
 - Compound units: ``10 m/s to mph``
 - Conversion errors: ``1 liter to volt``

## Varables
 - Previous answer: `ans + 2`
 - Variable assignment: `a = 143`


# 🌹 Additional Notes

## Unit Conversion

The conversion operator `to` converts its left argument to the *unit* of its right argument, ignoring its value. For example, `5m to mi` and `5m to 10mi` are identical.


## Celsius and Fahrenheit

Celsius and Fahrenheit are not supported as first-class units because they require an offset when converting from other temperature units. This leads to ambiguity when adding units, since one temperature must be seen as a *difference* rather than an absolute temperature.

Daisy instead provides four functions (`fromCelsius`, `toCelsius`, `fromFahrenheit`, `toFahrenheit`) which convert between scalars and Kelvin.
 - "from" functions take a scalar and return a value in Kelvin: `fromCelsius(0) = 273.15K`
 - "to" functions take a value in Kelvin and return a scalar: `toCelsius(273.15 K) = 0`

Functions `FtoC` and `CtoF` are also provided:
 - `FtoC(x) = toCelsius(fromFahrenheit(x))`
 - `CtoF(x) = toFahrenheit(fromCelsius(x))`


## Multiplication Order

Implicit multiplication has a higher priority than division. `pi/2 radians` will parse as `pi/(2 radians)`. Type `(pi/2) radians` or `pi/2 * radians` to get 90 degrees.