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PrettyLambda

Dernière modification

Ajouté(e) :

> [new]
> I use the misc-fixed font instead of the default, so lambda-mode displayed what looked like a Korean character. You can fix it by adding to your .emacs:
>
> (setq lambda-symbol (string #x1d77a))


Using Character Composition

This page is about displaying the word ‘lambda’ using the Greek letter. See also PrettySymbol.


Library pretty-lambdada.el defines commands, including minor modes (local and global), that let you do this, either for specific modes or generally. The core display code is similar to the following snippet:

  (defun pretty-lambdas ()
    (font-lock-add-keywords
     nil `(("(\\(lambda\\>\\)"
            (0 (progn (compose-region (match-beginning 1) (match-end 1)
                                      ,(make-char 'greek-iso8859-7 107))
                      nil))))))

There are several versions of such snippets floating around. The one above is from LawrenceMitchell, modified from StefanMonnier’s rewrite of OliverScholz’s rewrite of LukeGorrie’s original pretty-lambda.el code (http://fresh.homeunix.net/~luke/misc/emacs/pretty-lambda.el).

And here is a variant by TrentBuck:

  (font-lock-add-keywords 'emacs-lisp-mode
    '(("(\\(lambda\\)\\>" (0 (prog1 ()
                               (compose-region (match-beginning 1)
                                               (match-end 1)
                                               ?λ))))))

I stopped using this hack [1] because Emacs was actually saving weird escape characters in my files such that when I reloaded them I’d still get lambda-symbols, even with this turned off. But it makes the files unreadable to other programs. Does anyone else have this problem, and know the fix? Since it’s all done in font-lock I didn’t expect the saved files to be affected. – LukeGorrie

This should happen only if the file was saved in the coding system Emacs Mule, because emacs-mule preserves the composition property. (Composition is actually part of Emacs’ m17n support.) Normally you should not use emacs-mule; however, auto-save files are saved in that coding system. So if you restore a file after a crash, for instance, you can get something like what you describe. A fix would be to use a hook to remove all composition properties before auto-saving. – OliverScholz

Using Font-Lock and Overlays

This library defines a minor mode that uses font-lock and overlays to display ‘lambda’ as the Greek letter: http://dishevelled.net/elisp/lambda-mode.el.

I use the misc-fixed font instead of the default, so lambda-mode displayed what looked like a Korean character. You can fix it by adding to your .emacs:

    (setq lambda-symbol (string #x1d77a))

Using an Image

Sugawara offers another approach: a minor mode that displays ‘lambda’ as a large Greek letter using an image.

  (defvar big-lambda-image
    (create-image
     (base64-decode-string
      "/9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAsICAoIBwsKCQoNDAsNERwSEQ8PESIZGhQcKSQrKigk
  JyctMkA3LTA9MCcnOEw5PUNFSElIKzZPVU5GVEBHSEX/2wBDAQwNDREPESESEiFFLicuRUVFRUVF
  RUVFRUVFRUVFRUVFRUVFRUVFRUVFRUVFRUVFRUVFRUVFRUVFRUVFRUVFRUX/wAARCAAwAEADASIA
  AhEBAxEB/8QAGgABAQEBAAMAAAAAAAAAAAAAAAUEAwIGB//EACgQAAEEAQIEBgMAAAAAAAAAAAEA
  AgMEERIhBTFhcQYUIjJBgRVRkf/EABcBAQEBAQAAAAAAAAAAAAAAAAABAwL/xAAcEQEBAQACAwEA
  AAAAAAAAAAAAAQIRIQMxQVH/2gAMAwEAAhEDEQA/APriIiAThZqvEKd5zxUtQzmP3CN4dj+Lyu1G
  XqklaRzmxyDDtJwSM7jsRsehWHiUbKlrh1qJgYWTCu7TtmN/p09g7QfpaYznXX1FVERZqIiICIiA
  ofiK6IvJV2t1vdZhkfv7I2yNy4/ZAHforM80deCSaZ4ZHG0uc48gBuSoTqE13g1+1Kwi5dj1MYec
  bW7xs+uZ6krfwyTU1r0lewIuNOyy5ThsR+yZgeOxGV2WNnF4qiIigIiIJd+N/EL8NIsd5WPE87iN
  n4PoZ13GT0AHyqiIurrmSfgixT/gpJa9hjxRc4vgmYwuEeTksdgbYJJB5YOPjffQuOvNllETo4Ne
  InPBaZG4GXYO4Gc4/eMrWi61ua7s7QREWav/2Q==")
     'jpeg t))
  
  (defvar big-lambda-font-lock-keywords
    '((".+" (0 (prog1 nil
                 (big-lambda-remove-region
                  (match-beginning 0) (match-end 0)))))
      ("(\\(lambda\\)\\>"
       (0 (prog1 nil
            (big-lambda-region (match-beginning 1) (match-end 1)))))))
  
  (defun big-lambda-remove-region (beg end)
    "Remove big lambda property in region between BEG and END."
    (let (pos)
      (while (setq pos (text-property-any beg end 'display big-lambda-image))
        (remove-text-properties
         pos
         (or (next-single-property-change pos 'display) end)
         '(display)))))
  
  (defun big-lambda-region (beg end)
    "Add big lambda property in region between BEG and END."
    (put-text-property beg end 'display big-lambda-image))
  
  (define-minor-mode big-lambda-mode
    "Display big lambda."
    :lighter " Lambda"
    (if big-lambda-mode
        (progn
          (save-restriction
            (widen)
            (let ((font-lock-keywords big-lambda-font-lock-keywords))
              (font-lock-fontify-buffer)))
          (font-lock-add-keywords nil big-lambda-font-lock-keywords))
      (font-lock-remove-keywords nil big-lambda-font-lock-keywords)
      (save-restriction
        (widen)
        (let ((modified-p (buffer-modified-p)))
          (big-lambda-remove-region (point-min) (point-max))
          (set-buffer-modified-p modified-p)))))
  
  (defun big-lambda-mode-turn-on ()
    "Turn on `big-lambda-mode'."
    (interactive)
    (big-lambda-mode 1))
  
  (add-hook 'emacs-lisp-mode 'big-lambda-mode-turn-on)

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