# Code Staging in GNU Guix

Date: 2022-06-11 17:36:08 +08:00Date modified: 2022-06-11 18:10:24 +08:00>

- describes the code staging process for package definitions in Guix package manager; mainly describing roam:Guix G-expressions

- creating package definitions often certain parts of the definitions to carry through the build stage; oftentimes, these parts of code include additional build instructions for non-trivial packages and additional inputs for that package

- while S-expressions (sexp) are nice, they can be verbose at times; this is where G-expressions (gexp) comes in handy

  - gexp are hygenic — they preserve lexical scope across different stages

  - they can easily refer to the high-level objects (e.g., packages, local file) in the store (i.e., `/gnu/store`)

  - first-class Scheme values

  - binds deployment to staging — when brought into staging, all inputs are also deployed as well

- use cases for gexps

  - code sharing between multiple stages; this is mostly present such as defining packages and building them

  - cross-compilation — there are additional operators to denote "nativeness" where it will refer to the "native" version rather than the target version

  - package definitions — less verbose definitions which is always nice especially with the use of referring to the absolute file names from the store

  - system services — the process and lifecycle of system services is similar to defining packages being composed of multiple stages: one in definition and one in building the services in the init system

  - system tests — they can be defined through the `operating-system` interface which are derivations describing entire operating systems; in Guix, this is implemented through a tool called `marionette` which introduces another stage in the pipeline