Update 11-nix.qmd

11-nix.qmd

@@ -100,7 +100,66 @@ let
       
   }
 ```
+Thi first line imports a specfic hash of nixpkgs (pinning):
 
-I won’t go into much detail, but here are some pointers:
+```
+pkgs = import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/976fa3369d722e76f37c77493d99829540d43845.tar.gz") {};
+```
+
+Then, I define the set of R packages that we require:
+
+```
+rpkgs = builtins.attrValues {
+  inherit (pkgs.rPackages) quarto Ecdat devtools janitor plm pwt9 rio targets tarchetypes testthat tidyverse usethis formatR;
+};
+```
+
+I then do something similar for LaTeX packages:
+
+```
+tex = (pkgs.texlive.combine {
+  inherit (pkgs.texlive) scheme-small amsmath framed fvextra environ fontawesome5 orcidlink pdfcol tcolorbox tikzfill;
+});
+```
+
+Finally, I define the set of "system" packages, so the R language itself, and Quarto (and glibcLocalesUtf8 to set the locale variables
+to utf-8):
+
+```
+system_packages = builtins.attrValues {
+  inherit (pkgs) R glibcLocalesUtf8 quarto;
+};
+```
+
+Finally, all these definitions are used to define a *shell*:
+
+```
+in
+pkgs.mkShell {
+  LOCALE_ARCHIVE = if pkgs.system == "x86_64-linux" then "${pkgs.glibcLocalesUtf8}/lib/locale/locale-archive" else "";
+  LANG = "en_US.UTF-8";
+  LC_ALL = "en_US.UTF-8";
+  LC_TIME = "en_US.UTF-8";
+  LC_MONETARY = "en_US.UTF-8";
+  LC_PAPER = "en_US.UTF-8";
+  LC_MEASUREMENT = "en_US.UTF-8";
+
+  buildInputs = [rpkgs tex system_packages];
+}
+```
+
+In this block, a Nix shell environment is defined using pkgs.mkShell. The LOCALE_ARCHIVE variable is conditionally set based on the system architecture. 
+Several environment variables (LANG, LC_ALL, LC_TIME, LC_MONETARY, LC_PAPER, and LC_MEASUREMENT) are set to "en_US.UTF-8". 
+The buildInputs attribute specifies the list of inputs needed for this shell environment, which includes the three sets defined above: R packages (rpkgs), 
+TeX packages (tex), and system packages (system_packages).
+
+This Nix expression defines a development environment with specific R and TeX packages, system packages, and locale settings. 
+When this expression is evaluated using Nix, it will generate a shell environment that includes all the specified dependencies, 
+allowing you to work with R and TeX in a controlled and reproducible environment.
+
+This environment can be built using the `nix-build` command, and users can then *drop* into that shell using `nix-shell`. 
+
+Writing these Nix expressions is not easy, and there is a lot of boilerplate code. To simplify the process of writing these expressions,
+a package I wrote, called `{rix}`, can help you.
 
 ## The {rix} package