**[Try online!] • [Documentation] • [Tutorial] • [Syntax reference] • [Installation] • [Discord] • [Development]** [Try online!]: https://numbat.dev/ [Features]: #key-features [Documentation]: https://numbat.dev/docs/ [Tutorial]: https://numbat.dev/docs/tutorial/ [Syntax reference]: https://numbat.dev/docs/examples/example-numbat_syntax/ [Installation]: https://numbat.dev/docs/cli/installation/ [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/docs/advanced/type-system/) 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/docs/basics/unit-notation/) (`km/h` or `kilometer/hour`, `GiB` or `gibibytes`, `°` or `degree`, `m²` or `m^2`). New units can be [introduced](https://numbat.dev/docs/advanced/unit-definitions/) on the spot (`unit pixel`). Compatible units can be converted easily [using the `->` operator](https://numbat.dev/docs/basics/conversions/) (`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/docs/prelude/) 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/docs/prelude/list-units/) for a complete overview. It also contains a lot of [mathematical and physical constants](https://numbat.dev/docs/prelude/list-constants/) as well as a large range of [pre-defined functions](https://numbat.dev/docs/prelude/functions/).
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/main/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/main/numbat/modules) itself. It is therefore easily extensible by [providing a `init.nbt` file](https://numbat.dev/docs/cli/customization/). 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/docs/cli/installation/) 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/docs/cli/customization/#module-paths) for the standard paths on other operating systems). ## Contact us This project is maintained by [David Peter](https://github.com/sharkdp). 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).