special characters

Special characters

Living in a post-ASCII world offers great opportunities, but brings some
problems, too. After all, it's nice to be able to write Ångström or
Καλημέρα or ☺☎☯, but it's not necessarily easy to enter those
characters.

input methods

So - what to do? First, you can set the input-method, as explained in the emacs manual. This is the best solution if you're writing a non-Latin
language – Russian, Thai, Japanese, …

If you only occasionally need some accented character, input methods like
latin-postfix (e" -> ë), latin-prefix ("e -> ë) or TeX (\"e -> ë) are
useful. They also tend to annoy me a bit, as they often assume I need an
accented character, when all I want is to put a word in quotation marks…

compose key

Another method is to use a special compose key; for example, under Gnome 3
it's in the the Region and Language applet, under Options..., in Gnome 2
it's in the Keyboard applet in Layouts/Options…. This works for all
programs, not just emacs (see this Ubuntu help page for some details). I've
set my Compose-key to Right-Alt, so Right-Alt "e -> ë.

Using the compose key works pretty well for me; setting the input method may
be more convenient when you need to write a lot of accented characters.

Now, his may be good and well for the accented characters and other variants
of Latin characters, such as the German Ess-Zet ligature "ß" (note, you can
get that character with latin-prefix "s -> ß, latin-postfix s" -> ß or
<compose-key> ss -> ß). But what about Greek characters? Mathematical
symbols? Smileys?

ucs-insert

One way to add characters like α, ∞ or ☺ is to use ucs-insert, by
default bound to C-x 8 RET. If you know the official Unicode name for a
character, you can find it there; note that there's auto-completion and you
can use * wild-cards. For the mentioned characters, that would be GREEK SMALL LETTER ALPHA, INFINITY and WHITE SMILING FACE.

You can also use the Unicode code points; so C-x 8 RET 03b1 RET will insert
α as well, since its code point is U+03B1. In case you don't know the code
points of Unicode characters, a tool like the Character Map (gucharmap) in
Gnome may be useful.

abbrev

Since ucs-insert may not be convenient in all cases, you may want to add
shortcuts for oft-used special characters to you abbrev table. See the
entry on Abbrevs in the emacs manual. I usually edit the entries by hand with
M-x edit-abbrevs, and I have entries like:

(text-mode-abbrev-table)
"Delta0"       0    "Δ"
"^2"           0    "²"
"^3"           0    "³"
"almost0"      0    "≈"
"alpha0"       0    "α"
"any0"         0    "∀"
"beta0"        0    "β"
"c0"           0    "©"
"deg0"         0    "℃"
"delta0"       0    "δ"
"elm0"         0    "∈"
"epsilon0"     0    "ε"
"eta0"         0    "η"
"heart0"       0    "♥"
"inf0"         0    "∞"
"int0"         0    "∫"
"notis0"       0    "≠"

Now, alpha0 will be auto-replaced with α. I'm using the 0 suffix for
most entries so I can easily remember them, without making it hard to use
alpha as a normal word. Note, abbrevs are a bit picky when it comes to
the characters in the shortcut – for example, setting != -> ≠ won't
work.

inheriting abbrevs from other modes

If you have set up a nice set of abbreviations for text-mode, you may want
to use them in other modes as well; you can accomplish this by including the
text-mode abbreviations into the table for the current one, for example in
your ERC setup:

;; inherit abbrevs from text-mode
(abbrev-table-put erc-mode-abbrev-table :parents (list text-mode-abbrev-table))