99 lines
3.5 KiB
Markdown
99 lines
3.5 KiB
Markdown
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## Use cases
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This page lists some possible use cases for nix-cl.
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## Pinning down the exact commits of libraries
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Sometimes, a bug is fixed upstream but is not yet available in package
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repositories such as Quicklisp or Ultralisp. The users have to wait
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for the repository maintainer to update it, or download and compile
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the patched sources themselves.
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This is a manual and hard to reproduce process. By leveraging Nix,
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users of `nix-cl` can essentially "run their own package repository",
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written as Nix code, with all the benefits of that (shareability,
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cacheability, reproducibility, version-controllable etc.)
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## Modifying libraries with patches
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Other times, a bug in a library is not fixed upstream, but you fixed
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it yourself. Or, you would like a change to the internals that the
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maintainers don't like.
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Sure, you could fork the code or maintain patches manually, but that
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becomes hard to manage with a lot of patches. It also doesn't have the
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benefits mentioned in the previous section.
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`nix-cl` provides a way of applying version-controlled patches to any
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package.
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## Using libraries not available in repositories
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There are useful and working libraries out there, that are nontheless
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unavailable to users of package managers such as Quicklisp or
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Ultralisp. Two real-world examples are [jzon] and [cl-tar].
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`nix-cl` is not tied to any particular package source: instead,
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packages are written as a Nix expression, which can be done manually
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or generated/imported.
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This frees the user to have any package they want, and not be
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constrained by a central repository.
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## Reproducible environments
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The usual way to develop a project involves several steps, such as:
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1. Installing a Lisp implementation
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2. Installing a package manager
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3. Installing the chosen libraries
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This is not necessarily reproducible. It's unlikely to come back a
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year later and develop the project using the exact same versions of
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the dependencies.
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Things can break between attempts at different points in time. The
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repository could have updated versions in the meantime. The source
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tarballs could become unreachable.
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With `nix-cl` you can have your own binary cache for Lisp libraries
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and not be affected by downtime of other central repositories.
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## Testing across CL implementations
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One can manually download different Lisp implementations and run tests
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of a package. This works well in most cases, but it is limited in how
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you can tweak the software. Some practical examples are:
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- Statically compiling [zlib] into [SBCL]
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- Building SBCL with the `--fancy` flag
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- Compiling [ECL] as a static library
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These are usually hard to do manually, unless you have the necessary
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compilers already configured. These combinations are usually not
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available from package managers as well.
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With Nix it's easier, because it will set up the build environment
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automatically. It could be useful to, for example:
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- Test against all possible compiler flag combinations
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- Libc versions (ECL)
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- JDK versions ([ABCL])
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[zlib]: https://zlib.net
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[SBCL]: https://sbcl.org
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[ECL]: https://ecl.common-lisp.dev/
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[Ultralisp]: https://ultralisp.org/
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[jzon]: https://github.com/Zulu-Inuoe/jzon
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[cl-tar]: https://gitlab.common-lisp.net/cl-tar/cl-tar
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[bootstrap tools]: https://github.com/NixOS/nixpkgs/tree/master/pkgs/stdenv/linux/bootstrap-files
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[nixpkgs]: https://github.com/NixOS/nixpkgs
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## Windows note
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Note that all of this still only applies to Unix systems - primarily because Nix doesn't work on Windows.
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If you have an idea how to port some of the functionality to Windows, get in touch.
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