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The theme modus-vivendi exports an alist of named colors:

(deftheme modus-vivendi
    "Elegant, highly legible and customizable dark theme.
Conforms with the highest legibility standard for color contrast
between background and foreground in any given piece of text,
which corresponds to a minimum contrast in relative luminance of
7:1 (WCAG AAA standard).")

  (defconst modus-vivendi-palette
    '(
;;; Basic values

      (bg-main          "#000000")
      (bg-dim           "#1e1e1e")
      (fg-main          "#ffffff")
      (fg-dim           "#989898")
      (fg-alt           "#c6daff")
      ...

I am trying to access these colors by name so that I can use them in some face specifications. Here is the working code that I came up with:

(let-alist modus-vivendi-palette
  (let ((code-bg (car .bg-blue-nuanced)))
    (custom-set-faces
     `(org-block-begin-line ((t (:background ,code-bg :extend t))))
     `(org-block-end-line ((t (:background ,code-bg :extend t))))
     `(org-block ((t (:background ,code-bg :extend t))))
     )))

I am a new Lisp programmer who is used to languages such as Python, Java and JavaScript. This solution feels wrong to me because it requires a lot of work just to get some data from the equivalent of a Python dictionary. Is there a better way to implement this code, or is this considered idiomatic?

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  • First, if you're interested in developing your elisp chops, you may find dash.el useful. It's in both the Gnu and MELPA repos. The downside is that you've introduced a dependency and your code is no longer portable/vanilla elisp, but dash is very widely known and used, so that's not a big risk. It's a library of functional list-processing functions and Lisp macros. You may find you already have it installed as lots of packages use it. Anyway, the -let macro from dash.el could condense your first two lines into one.
    – Phil Hudson
    Commented Feb 14, 2023 at 17:45
  • Second, you have the identical expression being repeatedly assembled and assigned to the three faces. I would do it once using let (or -let) to assign that expression to a variable named say my-face-def. You then assemble each face redefinition thus: `(org-block ,my-face-def)
    – Phil Hudson
    Commented Feb 14, 2023 at 17:49
  • I agree that both of these suggestions would improve the code, thank you.
    – firstname gklsodascb
    Commented Feb 15, 2023 at 2:06

1 Answer 1

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3

I'm not an experienced Lisp programmer but using alist-get makes your code look cleaner to me

(let ((code-bg (alist-get 'bg-blue-nuanced modus-vivendi-palette)))
  (custom-set-faces
   `(org-block-begin-line ((t (:background ,code-bg :extend t))))
   `(org-block-end-line ((t (:background ,code-bg :extend t))))
   `(org-block ((t (:background ,code-bg :extend t))))))
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4
  • modus-vivendi-palette is an alist by definition but not one by convention. the value retrieved from it by alist-get is something like ("#000000")
    – nichijou
    Commented Feb 8, 2023 at 12:49
  • @nichijou what is the difference between an alist by definition and an alist by convention?
    – firstname gklsodascb
    Commented Feb 8, 2023 at 14:58
  • 1
    You would normally write alist in the form of ((key1 . value2) (key2 . value2)), you can get value1 with (alist-get 'key1 alist). The code you provide ((key1 value1) (key2 value2), actually is ((key1 . (value1)) (key2 . (value2))), with alist-get, you receive (value1), you have to further use car to get value1 out.
    – nichijou
    Commented Feb 8, 2023 at 15:42
  • That is very helpful information, thank you.
    – firstname gklsodascb
    Commented Feb 8, 2023 at 22:25

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