Nix Language

To broaden my knowledge of nix, I’m working through an Overview of the Nix Language.

Most of the data types and structures are relatively self-explanatory in the context of modern programming languages.

Double single quotes strip leading spaces.

''  s  '' == "s  "

Functions are a bit unexpected visually, but simply enough with an accompanying explanation. For example, the following is a named function f with two arguments x and y.

f = x: y: x*y

To call the function, write f 1 4. Calling the function with only a single arg returns a partial.

f 3
# returns `y: 3*y`

The with statement introduces values the scope of the expression so, you don’t need to use the dot notation.

let
  set = { a = 4; b = 10; };
in
  with set; "The values are ${toString a} and ${toString b}"

Values defined in a with statement do not override already defined values with the same name.

The rec expression turns a basic set into a set where self-referencing is possible.

rec {
    val1 = val2 + 100;
    val2 = 12;
}.val1
# outputs 112

nix repl can be used to test out statements in the Nix language.