Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/propensive/cardinality

Dependently-typed range-checked numbers for Scala
https://github.com/propensive/cardinality

dependent-types refined-types scala static-checks typesafe

Last synced: 25 days ago
JSON representation

Dependently-typed range-checked numbers for Scala

Awesome Lists containing this project

README 

        
[GitHub Workflow](https://github.com/propensive/cardinality/actions)

[](https://discord.com/invite/MBUrkTgMnA)




# Cardinality



__Constraints for constraining sets of real numbers__



_Cardinality_ introduces numerically-constrained `Double` types which are as usable as ordinary `Double`s, but safely constrained to a range that

is specified in their type.



## Features



- introduces `Double`s which are constrained to a numeric range, checked at compile time

- intuitive `a ~ b` syntax for representing a ranged `Double`

- ordinary `Double` literals can be used in positions which expect a ranged type

- numeric ranges compose under arithmetic operations

- escape-hatch (called `force`) for unsafe but easy conversions



## Availability



## Getting Started



_Cardinality_ provides a representation of numbers which must lie within a certain (closed) range. A range type is written with the

infix `~` type operator, between two doubles, for example, `-1.0 ~ 1.0` represents a `Double` which is at least `-1.0` and at most

`1.0`.



Compiletime operations check `Double` literals for conformance to the claimed bounds, for example:

```scala

val x: 0.0 ~ 100.0 = 33.3 // good

val y: 0.0 ~ 1.0 = 2.0    // compile error

```



Standard arithmetic operations are also implemented on ranged `Double`s. Depending on whether the right-hand operand is a statically-unknown

`Double`, a `Double` singleton literal, or a ranged `Double`, the result will be typed as precisely as possible. For example, adding `10.0` to

an instance of `3.0 ~ 5.0` will produce a result of type, `13.0 ~ 15.0`. These operations use typelevel arithmetic to calculate the resultant

range of the calculation, and can be composed like other arithmetic functions, with the return type inferred. For example,

```scala

var x: 0.0 ~ 1.0 = 0.2

var y: -1.0 ~ 1.0 = 0.2

var z: 1e3 ~ 1e8 = 10000



val result = (x + y*3.0)*z

```

will infer the type of `result` to be `-2.0e8 ~ 3.0e8` (while its value will be `6000.0`.



### Forcing values



Unranged `Double`s are pervasive in Scala, so a `Double#force` extension method is provided which can be used (carefully) to convert a `Double`

to an expected ranged type.



## Status



Cardinality is classified as __embryotic__. For reference, Soundness projects are

categorized into one of the following five stability levels:



- _embryonic_: for experimental or demonstrative purposes only, without any guarantees of longevity

- _fledgling_: of proven utility, seeking contributions, but liable to significant redesigns

- _maturescent_: major design decisions broady settled, seeking probatory adoption and refinement

- _dependable_: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version `1.0.0` or later

- _adamantine_: proven, reliable and production-ready, with no further breaking changes ever anticipated



Projects at any stability level, even _embryonic_ projects, can still be used,

as long as caution is taken to avoid a mismatch between the project's stability

level and the required stability and maintainability of your own project.



Cardinality is designed to be _small_. Its entire source code currently consists

of 147 lines of code.



## Building



Cardinality will ultimately be built by Fury, when it is published. In the

meantime, two possibilities are offered, however they are acknowledged to be

fragile, inadequately tested, and unsuitable for anything more than

experimentation. They are provided only for the necessity of providing _some_

answer to the question, "how can I try Cardinality?".



1. *Copy the sources into your own project*

   

   Read the `fury` file in the repository root to understand Cardinality's build

   structure, dependencies and source location; the file format should be short

   and quite intuitive. Copy the sources into a source directory in your own

   project, then repeat (recursively) for each of the dependencies.



   The sources are compiled against the latest nightly release of Scala 3.

   There should be no problem to compile the project together with all of its

   dependencies in a single compilation.



2. *Build with [Wrath](https://github.com/propensive/wrath/)*



   Wrath is a bootstrapping script for building Cardinality and other projects in

   the absence of a fully-featured build tool. It is designed to read the `fury`

   file in the project directory, and produce a collection of JAR files which can

   be added to a classpath, by compiling the project and all of its dependencies,

   including the Scala compiler itself.

   

   Download the latest version of

   [`wrath`](https://github.com/propensive/wrath/releases/latest), make it

   executable, and add it to your path, for example by copying it to

   `/usr/local/bin/`.



   Clone this repository inside an empty directory, so that the build can

   safely make clones of repositories it depends on as _peers_ of `cardinality`.

   Run `wrath -F` in the repository root. This will download and compile the

   latest version of Scala, as well as all of Cardinality's dependencies.



   If the build was successful, the compiled JAR files can be found in the

   `.wrath/dist` directory.



## Contributing



Contributors to Cardinality are welcome and encouraged. New contributors may like

to look for issues marked

[beginner](https://github.com/propensive/cardinality/labels/beginner).



We suggest that all contributors read the [Contributing

Guide](/contributing.md) to make the process of contributing to Cardinality

easier.



Please __do not__ contact project maintainers privately with questions unless

there is a good reason to keep them private. While it can be tempting to

repsond to such questions, private answers cannot be shared with a wider

audience, and it can result in duplication of effort.



## Author



Cardinality was designed and developed by Jon Pretty, and commercial support and

training on all aspects of Scala 3 is available from [Propensive

OÜ](https://propensive.com/).



## Name



The _cardinality_ of a set is the number of elements it contains, while _Cardinality_ controls the size of sets of `Double`s.



In general, Soundness project names are always chosen with some rationale,

however it is usually frivolous. Each name is chosen for more for its

_uniqueness_ and _intrigue_ than its concision or catchiness, and there is no

bias towards names with positive or "nice" meanings—since many of the libraries

perform some quite unpleasant tasks.



Names should be English words, though many are obscure or archaic, and it

should be noted how willingly English adopts foreign words. Names are generally

of Greek or Latin origin, and have often arrived in English via a romance

language.



## Logo



The logo shows the hat typically worn by a cardinal, alluding to the name _Cardinality_.



## License



Cardinality is copyright © 2024 Jon Pretty & Propensive OÜ, and

is made available under the [Apache 2.0 License](/license.md).