3 files changed, 99 insertions, 0 deletions
diff --git a/users/wpcarro/emacs/pkgs/vector/default.nix b/users/wpcarro/emacs/pkgs/vector/default.nix
new file mode 100644
index 000000000000..c0a475aaaa82
--- /dev/null
+++ b/users/wpcarro/emacs/pkgs/vector/default.nix
@@ -0,0 +1,21 @@
+{ pkgs, depot, ... }:
+
+let
+  vector = pkgs.callPackage
+    ({ emacsPackages }:
+      emacsPackages.trivialBuild {
+        pname = "vector";
+        version = "1.0.0";
+        src = ./vector.el;
+      })
+    { };
+
+  emacs = (pkgs.emacsPackagesFor pkgs.emacs28).emacsWithPackages (epkgs: [ vector ]);
+in
+vector.overrideAttrs (_old: {
+  doCheck = true;
+  checkPhase = ''
+    ${emacs}/bin/emacs -batch \
+      -l ert -l ${./tests.el} -f ert-run-tests-batch-and-exit
+  '';
+})
diff --git a/users/wpcarro/emacs/pkgs/vector/tests.el b/users/wpcarro/emacs/pkgs/vector/tests.el
new file mode 100644
index 000000000000..ffa983188229
--- /dev/null
+++ b/users/wpcarro/emacs/pkgs/vector/tests.el
@@ -0,0 +1,20 @@
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Dependencies
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(require 'ert)
+(require 'vector)
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Tests
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(ert-deftest vector-misc-tests ()
+  (let ((xs [1 2 3])
+        (ys [1 2 3]))
+    (should (= 1 (vector-get 0 ys)))
+    (vector-set 0 4 ys)
+    (should (= 1 (vector-get 0 ys)))
+    (should (= 1 (vector-get 0 xs)))
+    (vector-set! 0 4 xs)
+    (should (= 4 (vector-get 0 xs)))))
diff --git a/users/wpcarro/emacs/pkgs/vector/vector.el b/users/wpcarro/emacs/pkgs/vector/vector.el
new file mode 100644
index 000000000000..87f38d7d93e2
--- /dev/null
+++ b/users/wpcarro/emacs/pkgs/vector/vector.el
@@ -0,0 +1,58 @@
+;;; vector.el --- Working with Elisp's Vector data type -*- lexical-binding: t -*-
+
+;; Author: William Carroll <wpcarro@gmail.com>
+;; Version: 0.0.1
+;; Package-Requires: ((emacs "25.1"))
+
+;;; Commentary:
+;; It might be best to think of Elisp vectors as tuples in languages like
+;; Haskell or Erlang.
+;;
+;; Not surprisingly, this API is modelled after Elixir's Tuple API.
+;;
+;; Some Elisp trivia:
+;; - "Array": Usually means vector or string.
+;; - "Sequence": Usually means list or "array" (see above).
+;;
+;; It might be a good idea to think of Array and Sequence as typeclasses in
+;; Elisp.  This is perhaps more similar to Elixir's notion of the Enum protocol.
+;;
+;; Intentionally not supporting a to-list function, because tuples can contain
+;; heterogenous types whereas lists should contain homogenous types.
+
+;;; Code:
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Library
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defun vector-concat (&rest args)
+  "Return a new vector composed of all vectors in `ARGS'."
+  (apply #'vconcat args))
+
+(defun vector-prepend (x xs)
+  "Add `X' to the beginning of `XS'."
+  (vector-concat `[,x] xs))
+
+(defun vector-append (x xs)
+  "Add `X' to the end of `XS'."
+  (vector-concat xs `[,x]))
+
+(defun vector-get (i xs)
+  "Return the value in `XS' at index, `I'."
+  (aref xs i))
+
+(defun vector-set (i v xs)
+  "Set index `I' to value `V' in `XS'.
+Returns a copy of `XS' with the updates."
+  (let ((copy (vconcat [] xs)))
+    (aset copy i v)
+    copy))
+
+(defun vector-set! (i v xs)
+  "Set index `I' to value `V' in `XS'.
+This function mutates XS."
+  (aset xs i v))
+
+(provide 'vector)
+;;; vector.el ends here