Spelling check in Emacs 25.2 on Mac OS Sierra

Question

I am new to Emacs and I have a hard time to have spelling check when I use Emacs+AUCTex.

Here is a list of what I have done so far:

1. I read on a post saying that I should not install Flyspell. So I did not.
2. I followed some instructions on Homebrew. I think I have installed ispell successfully.
3. When I tried to install aspell, it says Error: No available formula with the name "aspell-en".

Now when I use M-x ispell, it says Searching for program: No such file or directory, ispell.

I saw different solutions online and tried some, but none of them worked. And since I am new to Emacs, I also do not want to mess up my .emacs file too much. So I come here for some help.

Answer 1

Firstly you need to get aspell installed correctly. As mentioned in the comments "brew install aspell" should be all you need. If that doesn't work then you have a problem with brew. By default this will install the "aspell" executable (note that it's not called "ispell") into /usr/local/bin. You need to tell Emacs to use "aspell" instead of "ispell" which you can do by adding (setq ispell-program-name "/usr/local/bin/aspell") to your Emacs init file. Running M-x ispell should then run your aspell programme.

Answer 2

First, to install on brew just use brew install aspell, without the -en that is a dictionary file which you can install later (but the brew aspell comes with English). Then go to Terminal and type which aspell it should tell you where aspell is installed. If it gives you a directory you can actually type aspell check textfile.txt (insert a text file name in that directory) to check its operation. After that Emacs should figure itself out. If not then you need to do a quick check for setup file settings again.

Answer 3

flyspell is an independent minor mode which use a few APIs from ispell. So you are actually using flyspell instead of ispell to do the spelling check.

1. flyspell is built in package of Emacs. You don't need install it manually

2. "I think I have installed ispell successfully" doesn't make sense. You need install aspell and its dictionaries. Then you need tweak a few variables from ispell to actually use flyspell (as I mentioned, flyspell re-use a few APIs from ispell)

3. See https://github.com/Homebrew/homebrew-core/issues/2419 , make sure you have the right version of aspell installed from homebrew (try which aspell in shell)

After installing aspell and its dictionaries successfully, you need setup flyspell,

 (setq ispell-program-name "aspell")
 ;; Please note ispell-extra-args contains ACTUAL parameters passed to aspell
 (setq ispell-extra-args '("--sug-mode=ultra" "--lang=en_US")

Usage is simple, either M-x flyspell-buffer to manually check the buffer for once or M-x flyspell-mode to turn on on-the-fly spell checking.

See http://blog.binchen.org/posts/what-s-the-best-spell-check-set-up-in-emacs.html for details.