emacs's spell check feature problems (criticism)

[Xah Lee]

Some criticism about emacs spell checking feature.

• Emacs Spell Checker Problems
  http://xahlee.org/emacs/emacs_spell_checker_problems.html

plain text version follows:

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Emacs Spell Checker Problems

Xah Lee, 2010-05-25

This page discuss emacs's spell checking feature, its problems, and
some practical tips.

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flyspell-mode Problems

Emacs has a spell checking feature (flyspell-mode), that check
spelling errors while you type, much like all other modern editors,
word processors, email programs, or text box in browsers. However,
emacs's spell checking feature is much worse than the spell checker in
browsers or any commercial editor.

When you have flyspell-mode on, it slows down your editing noticeably.
Normally, when you hold down “Ctrl+→” (forward-word), the cursor moves
fast across lines to the place you want. But with flyspell on, the
cursor freezes, and when you release the key, the cursor shows in some
other place. Essentially, the screen is not updated so often. This is
just not workable.

Another problem is that if you open a document, with flyspell-mode on,
it does not automatically check the spelling of all existing text. I
think it only checks word at your cursor positions. (which explains
why you can't move cursor fast across words.)

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speck-mode

There is a alternative, called speck-mode, which i've been using since
~2007. Like other spell checking feature in commercial editors, it
does its work in the background quietly when you are not doing
anything. However, getting speck-mode setup isn't trivial, especially
on Windows, because you have to install the spell checking engine.
(one of ispell, aspell, hunspell) Basically, you need to be a emacs
expert to get it to work.

Also, in most commercial software, the spell checker will eventually
check the whole document, but speck-mode only checks texts that's
visible portion of the window. I haven't looked into if it is possible
to change this.


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speck-mode, Great Code, Bad Everything Else

speck-mode's author is Martin Rudalics, who seems to have published a
paper on Common Lisp in ACM back in 1989. (See: Distributed copying
garbage collection (1986) by Martin Rudalics, at Source) So,
apparently the guy seems to be a old lisper who knows what he's doing
as far as the code goes. However, speck-mode is one of those mode that
only few emacs people know or use. It lacks much documentation (it has
none!). Me and David Capello have made the whole spelling system work
with speck-mode in our ErgoEmacs distribution, out of the box. It
worked, better than flyspell, but isn't perfect. And i haven't really
put that much time into fixing issues. (See: issue 51, issue 56, issue
74. )

Today, doing some work on ErgoEmacs, i thought why not send a email to
Martin and see if there's a new version. Indeed, there is, and he send
it to me.

However, he told me that there even isn't a public location for the
mode. The one that appears on emacswiki at emacswiki SpeckMode is from
2008-07-26. Gah!

Here's the latest version speck.el 2010-05-25.

I tried to incorporate this version into ErgoEmacs, but run into
problems... gah. Will need to work on it, probably half a day. Here's
the error:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  intern(nil)
  (cond ((eq speck-engine ...) (intern speck-aspell-default-dictionary-
name)) ((eq speck-engine ...) (intern speck-hunspell-default-
dictionary-name)) ((eq speck-engine ...) (intern speck-ispell-default-
dictionary-name)))
  (or speck-saved-dictionary (cond (... ...) (... ...) (... ...)))
  (setq speck-dictionary (or speck-saved-dictionary
(cond ... ... ...)))
  (if (and (local-variable-p ...) speck-dictionary) nil (setq speck-
dictionary (or speck-saved-dictionary ...)))
  (unless (and (local-variable-p ...) speck-dictionary) (setq speck-
dictionary (or speck-saved-dictionary ...)))
  speck-activate()
  (if speck-mode (speck-activate) (speck-deactivate))
  (let ((last-message ...)) (setq speck-mode (cond ... ... ...)) (if
speck-mode (speck-activate) (speck-deactivate)) (run-hooks (quote
speck-mode-hook) (if speck-mode ... ...)) (if (called-interactively-p)
(progn nil ...)))
  speck-mode(toggle)
  call-interactively(speck-mode t nil)
  execute-extended-command(nil)
  call-interactively(execute-extended-command nil nil)


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OpenSource Spell-Checking Engines

Besides the bad quality of the spell checking feature, the open source
spell checking engine ispell and aspell are also much inferior than
commercial ones, lacking much words and commonly accepted spelling
variations, with the exception of Hunspell.

See Wikipedia: Hunspell. It is based on MySpell, which is based on
Ispell, and probably with input from Aspell. So, the Open Source spell
checking engines roughly goes from Ispell→Aspell→Hunspell. Note that
Hunspel is used by Firefox, Opera, Google Chrome, Apple Mac OS X.

See also: Problems of Open Source Dictionaries.

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How to Always Have Spell Checker On

A little practical tip. By default, spell checker isn't even on.
However, if you want it always on, you can put this code in your emacs
init file:

(defun turn-spell-checking-on ()
  "Turn speck-mode or flyspell-mode on."
  ;; (speck-mode 1)
  (flyspell-mode 1)
  )

(add-hook 'text-mode-hook 'turn-spell-checking-on)

Also, there's the command flyspell-buffer that checks the whole file,
but alas, it is slow. While it works, your emacs is frozen.

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  Xah
∑ http://xahlee.org/

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