{"id":16965062,"url":"https://github.com/propensive/mercator","last_synced_at":"2025-03-17T08:37:47.057Z","repository":{"id":165073674,"uuid":"615813686","full_name":"propensive/mercator","owner":"propensive","description":"Autogeneration of functor and monad instances for Scala types","archived":false,"fork":false,"pushed_at":"2025-02-05T19:46:28.000Z","size":1291,"stargazers_count":2,"open_issues_count":1,"forks_count":1,"subscribers_count":2,"default_branch":"main","last_synced_at":"2025-03-10T19:53:48.032Z","etag":null,"topics":["functors","monads","scala"],"latest_commit_sha":null,"homepage":"","language":"Scala","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":null,"status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/propensive.png","metadata":{"files":{"readme":".github/readme.md","changelog":null,"contributing":".github/contributing.md","funding":null,"license":null,"code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2023-03-18T18:49:58.000Z","updated_at":"2025-02-05T19:46:32.000Z","dependencies_parsed_at":"2023-10-12T15:27:52.865Z","dependency_job_id":"543f4b0d-526d-40a4-9276-e3c38b4128bf","html_url":"https://github.com/propensive/mercator","commit_stats":null,"previous_names":[],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/propensive%2Fmercator","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/propensive%2Fmercator/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/propensive%2Fmercator/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/propensive%2Fmercator/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/propensive","download_url":"https://codeload.github.com/propensive/mercator/tar.gz/refs/heads/main","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":243852499,"owners_count":20358271,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["functors","monads","scala"],"created_at":"2024-10-13T23:44:55.443Z","updated_at":"2025-03-17T08:37:47.045Z","avatar_url":"https://github.com/propensive.png","language":"Scala","funding_links":[],"categories":[],"sub_categories":[],"readme":"[\u003cimg alt=\"GitHub Workflow\" src=\"https://img.shields.io/github/actions/workflow/status/propensive/mercator/main.yml?style=for-the-badge\" height=\"24\"\u003e](https://github.com/propensive/mercator/actions)\n[\u003cimg src=\"https://img.shields.io/discord/633198088311537684?color=8899f7\u0026label=DISCORD\u0026style=for-the-badge\" height=\"24\"\u003e](https://discord.com/invite/MBUrkTgMnA)\n\u003cimg src=\"/doc/images/github.png\" valign=\"middle\"\u003e\n\n# Mercator\n\n__Autogeneration of functor and monad instances for Scala types__\n\nMercator makes it possible to abstract over monads and functors, automatically\nconstructing contextual instances for types with the requisite methods.\n\nThis allows generic implementations of `sequence` and `traverse` to be provided\nfor all types which define `map` and `flatMap`, provided an appropriate\nimplementation of `Point` (providing the monadic \"unit\" operation) can be found.\n\n## Features\n\n- provides an abstraction over functor-like and monad-like types\n- generates `Monad`, `Functor` and `Point` typeclasses for type constructors\n- constructs a monad typeclass instance for any type with `flatMap`, `map` and a \"unit\" constructor\n- implements `sequence` and `traverse` extension methods for instances of monadic types\n\n## Availability\n\n\n\n\n\n\n\n## Getting Started\n\nIt is not possible to write code such as,\n```\ndef increment[MonadicType[_]](xs: MonadicType[Int]) =\n  for(x \u003c- xs) yield x + 1\n```\nbecause the compiler is not able to express the constraint that the type\nconstructor `F[_]` provides the methods `map` and `flatMap` (with the correct\nsignatures), which are necessary for the for-comprehension to compile.\n\nWith _Mercator_, it is possible to demand a contextual instance of `Monad[MonadicType]` to\nenforce this constraint. Mercator will automatically instantiate such an\ninstance at the use-site for any type which has the required methods, like so,\n```\nimport mercator._\ndef increment[F[_]: Monad](xs: F[Int]) = for(x \u003c- xs) yield x + 1\n```\n\nThe methods `flatMap` and `map` will be provided to the instance of `F[_]` as\nextension methods, which are then used by the for-comprehension.\n\n## Point\n\nAn instance of `Monad[F]` will generate an implementation of `point` (sometimes\ncalled \"unit\", though not to be confused with `Unit`) which\nconstructs a new instance of the type from a single value. For example, `point(x)` for\n`Option` is `Some(x)`, or for `Either` it is `Right(x)`. This implementation\nassumes the existence of a unique `apply` method on the type's companion object, and\nthat applying the value to it will produce a result of the correct type.\n\nA `Point[MonadicType]` instance can always be provided to explicitly specify the\n`point` instance for the given type constructor.\n\n## Functors\n\nMercator also provides a `Functor` typeclass, which provides implementations of just\n`point` and `map`. If `map` is required for a particular operation, but `flatMap` is not,\nthen only the `Functor` typeclass should be summoned.\n\n\n\n\n## Status\n\nMercator is classified as __embryotic__. For reference, Soundness projects are\ncategorized into one of the following five stability levels:\n\n- _embryonic_: for experimental or demonstrative purposes only, without any guarantees of longevity\n- _fledgling_: of proven utility, seeking contributions, but liable to significant redesigns\n- _maturescent_: major design decisions broady settled, seeking probatory adoption and refinement\n- _dependable_: production-ready, subject to controlled ongoing maintenance and enhancement; tagged as version `1.0.0` or later\n- _adamantine_: proven, reliable and production-ready, with no further breaking changes ever anticipated\n\nProjects at any stability level, even _embryonic_ projects, can still be used,\nas long as caution is taken to avoid a mismatch between the project's stability\nlevel and the required stability and maintainability of your own project.\n\nMercator is designed to be _small_. Its entire source code currently consists\nof 240 lines of code.\n\n## Building\n\nMercator will ultimately be built by Fury, when it is published. In the\nmeantime, two possibilities are offered, however they are acknowledged to be\nfragile, inadequately tested, and unsuitable for anything more than\nexperimentation. They are provided only for the necessity of providing _some_\nanswer to the question, \"how can I try Mercator?\".\n\n1. *Copy the sources into your own project*\n   \n   Read the `fury` file in the repository root to understand Mercator's build\n   structure, dependencies and source location; the file format should be short\n   and quite intuitive. Copy the sources into a source directory in your own\n   project, then repeat (recursively) for each of the dependencies.\n\n   The sources are compiled against the latest nightly release of Scala 3.\n   There should be no problem to compile the project together with all of its\n   dependencies in a single compilation.\n\n2. *Build with [Wrath](https://github.com/propensive/wrath/)*\n\n   Wrath is a bootstrapping script for building Mercator and other projects in\n   the absence of a fully-featured build tool. It is designed to read the `fury`\n   file in the project directory, and produce a collection of JAR files which can\n   be added to a classpath, by compiling the project and all of its dependencies,\n   including the Scala compiler itself.\n   \n   Download the latest version of\n   [`wrath`](https://github.com/propensive/wrath/releases/latest), make it\n   executable, and add it to your path, for example by copying it to\n   `/usr/local/bin/`.\n\n   Clone this repository inside an empty directory, so that the build can\n   safely make clones of repositories it depends on as _peers_ of `mercator`.\n   Run `wrath -F` in the repository root. This will download and compile the\n   latest version of Scala, as well as all of Mercator's dependencies.\n\n   If the build was successful, the compiled JAR files can be found in the\n   `.wrath/dist` directory.\n\n## Contributing\n\nContributors to Mercator are welcome and encouraged. New contributors may like\nto look for issues marked\n[beginner](https://github.com/propensive/mercator/labels/beginner).\n\nWe suggest that all contributors read the [Contributing\nGuide](/contributing.md) to make the process of contributing to Mercator\neasier.\n\nPlease __do not__ contact project maintainers privately with questions unless\nthere is a good reason to keep them private. While it can be tempting to\nrepsond to such questions, private answers cannot be shared with a wider\naudience, and it can result in duplication of effort.\n\n## Author\n\nMercator was designed and developed by Jon Pretty, and commercial support and\ntraining on all aspects of Scala 3 is available from [Propensive\nO\u0026Uuml;](https://propensive.com/).\n\n\n\n## Name\n\nGerardus Mercator was a cartographer who developed a general method of\nprojecting a map of the surface of a sphere onto a flat surface, while\npreserving straight lines. Similarly, _Mercator_ provides `map` and `flatMap`\nmethods to objects which support them.\n\nIn general, Soundness project names are always chosen with some rationale,\nhowever it is usually frivolous. Each name is chosen for more for its\n_uniqueness_ and _intrigue_ than its concision or catchiness, and there is no\nbias towards names with positive or \"nice\" meanings—since many of the libraries\nperform some quite unpleasant tasks.\n\nNames should be English words, though many are obscure or archaic, and it\nshould be noted how willingly English adopts foreign words. Names are generally\nof Greek or Latin origin, and have often arrived in English via a romance\nlanguage.\n\n## Logo\n\nThe logo shows the lines of latitude of an [Oblique Mercator Projection](https://en.wikipedia.org/wiki/Oblique_Mercator_projection).\n\n## License\n\nMercator is copyright \u0026copy; 2025 Jon Pretty \u0026 Propensive O\u0026Uuml;, and\nis made available under the [Apache 2.0 License](/license.md).\n\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fpropensive%2Fmercator","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fpropensive%2Fmercator","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fpropensive%2Fmercator/lists"}