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https://github.com/sharkdp/numbat

A statically typed programming language for scientific computations with first class support for physical dimensions and units
https://github.com/sharkdp/numbat

calculator physics programming-language statically-typed terminal-based units web-app

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A statically typed programming language for scientific computations with first class support for physical dimensions and units

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README 

        






**[Try online!] • [Documentation] • [Tutorial] • [Syntax reference] • [Installation] • [Discord] • [Development]**



[Try online!]: https://numbat.dev/

[Features]: #key-features

[Documentation]: https://numbat.dev/doc/

[Tutorial]: https://numbat.dev/doc/tutorial.html

[Syntax reference]: https://numbat.dev/doc/example-numbat_syntax.html

[Installation]: https://numbat.dev/doc/cli-installation.html

[Discord]: https://discord.gg/kAaVTsat4D

[Development]: #development



*Numbat* is a statically typed programming language for scientific computations


with first class support for physical dimensions and units.






## Key Features






*Click to learn more.*



Physical dimensions as types






Numbat has a static type system where physical dimensions like `Length` and `Time` act as types.

Definitions of constants and functions can optionally contain type annotations that will be statically enforced.

If the types are not specified, they will be inferred (`Speed`, `Money` and `Frequency` in the screenshot).



See [this article](https://numbat.dev/doc/type-system.html) to learn more about Numbat's type system.



First-class physical units






Numbat is focused on computations with units. Units are therefore treated as first-class citizens. They can be

[entered in various ways](https://numbat.dev/doc/unit-notation.html) (`km/h` or `kilometer/hour`, `GiB` or

`gibibytes`, `°` or `degree`, `m²` or `m^2`).

New units can be [introduced](https://numbat.dev/doc/unit-definitions.html) on the spot (`unit pixel`).

Compatible units can be converted easily [using the `->` operator](https://numbat.dev/doc/unit-conversions.html) (`30 km/h -> mph`, `1 mrad -> degree`, `5 in + 2 ft -> cm`, `27 weeks -> days`).

And unit expressions are simplified using various heuristics (`15 km/h * 30 min = 7.5 km`).



Comprehensive standard library






Numbat's [standard library](https://numbat.dev/doc/prelude.html) comes with a large number of physical dimensions and units (SI, US Customary, Imperial, Nautical, Astronomical, Atomic, Nuclear, …).

See [this reference page](https://numbat.dev/doc/list-units.html) for a complete overview.

It also contains a lot of [mathematical and physical constants](https://numbat.dev/doc/list-constants.html)

as well as a large range of [pre-defined functions](https://numbat.dev/doc/list-functions.html).



Strict syntax






Numbat's parser never tries to be "smart" on syntactically incorrect input.

This means you will either get a (descriptive) error message, or you can trust the result of your calculation.



Excellent error messages






Numbat aims to provide [descriptive and helpful error messages](https://github.com/sharkdp/numbat/blob/master/assets/numbat-error.png).



Interactive terminal






Numbat has been designed for an interactive use-case with small "one off" computations. Opening the `numbat` interpreter

without any arguments starts a [REPL](https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop) with a familiar

readline interface, including all the usual features like a command history, Ctrl-R search or tab completion.



Modular and customizable






The whole system of physical dimensions and units is specified Numbat's standard library, which is

[written in the Numbat language](https://github.com/sharkdp/numbat/tree/master/numbat/modules) itself. It is therefore

easily extensible by [providing a `init.nbt` file](https://numbat.dev/doc/cli-customization.html). For example,

a single line (`unit bathtub = 150 L`) is usually enough to add a new unit. Users can even choose to write their

own `prelude` module, allowing for arbitrary modifications to the unit system.



Assertions






With its static type system, Numbat already enforces correctness of your calculations on a physical dimension level.

But some checks can only be made at runtime. Numbat provides an `assert_eq` procedure that allows you to check for

exact equality using `assert_eq(12 ft, 1 in)` or approximate equality using `assert_eq(c, 300_000 km/s, 1% × c)`.

This can be useful to make sure that intermediate results do not change during a restructuring of your calculation.



Non-features






Numbat is a scientific calculator. It's not a computer algebra system that solves differential equations

or computes intergrals. Try [WolframAlpha](http://www.wolframalpha.com/) instead.


There is no graphical user interface with buttons like `x²`, `1/x` or `DEG/RAD`.

[Qalculate!](http://qalculate.github.io/) is a fantastic tool that supports both text as well as graphical

input.


Numbat supports a huge range of physical units. If you need something even more comprehensive,

please consider contributing. Or try [GNU units](https://www.gnu.org/software/units/).



 


 


 


 



## Installation



See [this page](https://numbat.dev/doc/cli-installation.html) for details on how to install the native command-line version of Numbat.



## Development



[![CICD](https://github.com/sharkdp/numbat/actions/workflows/ci.yml/badge.svg)](https://github.com/sharkdp/numbat/actions/workflows/ci.yml)



Run Numbat CLI

```

cargo run -- 

```



Install the CLI version

```

cargo install -f --path numbat-cli

```



Run all tests

```

cargo test

```



### Working on the `prelude`



If you are working on [Numbat's standard library](numbat/modules/), it is convenient to point

the `NUMBAT_MODULES_PATH` environment variable to the `numbat/modules/` folder. This way,

you don't have to recompile Numbat to see your changes.



Alternatively, you can create a symlink from `~/.config/numbat/modules` to the `numbat/modules/`

folder in the repository (see [this page](https://numbat.dev/doc/cli-customization.html#module-paths)

for the standard paths on other operating systems).



## Contact us



To contact us, either [open a GitHub issue](https://github.com/sharkdp/numbat/issues/new/choose)

or [discussion](https://github.com/sharkdp/numbat/discussions), or pop into our

[Discord server](https://discord.gg/kAaVTsat4D).