sbcl'.pkgs.alexandria
```

## Overriding package attributes {#lisp-overriding-package-attributes}

Packages export the `overrideLispAttrs` function, which can be used to build a
new package with different parameters.

Example of overriding `alexandria`:

```nix
sbcl.pkgs.alexandria.overrideLispAttrs (oldAttrs: rec {
  version = "1.4";
  src = fetchFromGitLab {
    domain = "gitlab.common-lisp.net";
    owner = "alexandria";
    repo = "alexandria";
    tag = "v${version}";
    hash = "sha256-1Hzxt65dZvgOFIljjjlSGgKYkj+YBLwJCACi5DZsKmQ=";
  };
})
```

### Dealing with slashy systems {#lisp-dealing-with-slashy-systems}

Slashy (secondary) systems should not exist in their own packages! Instead, they
should be included in the parent package as an extra entry in the `systems`
argument to the `build-asdf-system`/`buildASDFSystem` functions.

The reason is that ASDF searches for a secondary system in the `.asd` of the
parent package. Thus, having them separate would cause either one of them not to
load cleanly, because one will contains FASLs of itself but not the other, and
vice versa.

To package slashy systems, use `overrideLispAttrs`, like so:

```nix
ecl.pkgs.alexandria.overrideLispAttrs (oldAttrs: {
  systems = oldAttrs.systems ++ [ "alexandria/tests" ];
  lispLibs = oldAttrs.lispLibs ++ [ ecl.pkgs.rt ];
})
```

See the [respective section](#lisp-including-external-pkg-in-scope) on using
`withOverrides` for how to weave it back into `ecl.pkgs`.

Note that sometimes the slashy systems might not only have more dependencies
than the main one, but create a circular dependency between `.asd`
files. Unfortunately, in this case an adhoc solution becomes necessary.

## Building Wrappers {#lisp-building-wrappers}

Wrappers can be built using the `withPackages` function of Common Lisp
implementations (`abcl`, `ecl`, `sbcl` etc.):

```
nix-shell -p 'sbcl.withPackages (ps: [ ps.alexandria ps.bordeaux-threads ])'
```

Such a wrapper can then be used like this:

```
$ sbcl
* (load (sb-ext:posix-getenv "ASDF"))
* (asdf:load-system 'alexandria)
* (asdf:load-system 'bordeaux-threads)
```

### Loading ASDF {#lisp-loading-asdf}

For best results, avoid calling `(require 'asdf)` When using the
library-generated wrappers.

Use `(load (ext:getenv "ASDF"))` instead, supplying your implementation's way of
getting an environment variable for `ext:getenv`. This will load the
(pre-compiled to FASL) Nixpkgs-provided version of ASDF.

### Loading systems {#lisp-loading-systems}

There, you can use `asdf:load-system`. This works by setting the right
values for the `CL_SOURCE_REGISTRY`/`ASDF_OUTPUT_TRANSLATIONS` environment
variables, so that systems are found in the Nix store and pre-compiled FASLs are
loaded.

## Adding a new Lisp {#lisp-adding-a-new-lisp}

The function `wrapLisp` is used to wrap Common Lisp implementations. It adds the
`pkgs`, `withPackages`, `withOverrides` and `buildASDFSystem` attributes to the
derivation.

`wrapLisp` takes these arguments:

- `pkg`: the Lisp package
- `faslExt`: Implementation-specific extension for FASL files
- `program`: The name of executable file in `${pkg}/bin/` (Default: `pkg.pname`)
- `flags`: A list of flags to always pass to `program` (Default: `[]`)
- `asdf`: The ASDF version to use (Default: `pkgs.asdf_3_3`)
- `packageOverrides`: Package overrides config (Default: `(self: super: {})`)

This example wraps CLISP:

```nix
wrapLisp {
  pkg = clisp;
  faslExt = "fas";
  flags = [
    "-E"
    "UTF8"
  ];
}
```