How to type pointer arrow -> in C quickly?
reddit / emacs

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J-ky · 2022-08-02 02:28

We often need to insert the arrow (->) to dereference the pointer and
access its member.

Is there a way to do this quickly?

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CorysInTheHouse69 · 2022-08-02 03:05

How would you want this done? Like through a key bind or you press a
key like “-“ and it inserts “->”?

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Schievel1 · 2022-08-02 04:25

I type - and then >.

But honestly, you can put that on a key chord. Is it worth it?

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azfrak · 2022-08-02 04:36

Using [key chords](https://github.com/emacsorphanage/key-chord)
(untested though)

    (require 'key-chord)
    (key-chord-mode 1)
    (key-chord-define c-mode-map "--"     "->")

then type `--` quickly and will insert pointer arrow, but of course
could change to any key chord that you like.

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J-ky · 2022-08-02 04:36

Since using shift for the ">" is a bit slow for me, I thought it would
be good to convert two consecutive dots into an arrow in C/C++.

I quickly put up a minor mode for that.

```
(defun shapeless-c-arrow-insert-dot ()
  (interactive)
  (if (looking-back "\\.")
      (progn
        (backward-delete-char 1)
        (insert "->"))
    (insert ".")))

(define-minor-mode shapeless-c-arrow-mode
  "Quickly insert arrow operator. ->"
  :keymap
  (let ((map (make-sparse-keymap)))
    (keymap-set map "." #'shapeless-c-arrow-insert-dot)
    map))

(add-hook 'c-mode-hook #'shapeless-c-arrow-mode)
(add-hook 'c++-mode-hook #'shapeless-c-arrow-mode)

```

Maybe it is a bit overkill.

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ndamee · 2022-08-02 05:59

Some people don't like shifted keys, because it slows down typing. I
too avoid unnecessary shifting if possible. It's more convenient,
especially in case of such operators which are used a lot.

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Schievel1 · 2022-08-02 07:29

Understandable.

You could put -> on - instead.
I think - alone isn’t used very often anyway in C.

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pajuch · 2022-08-02 10:11

Have no use for this currently but have added to my config.. Thanks

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nitroll · 2022-08-02 12:00

These lines has been in my configuration for a long time, there might
be smarter ways to do the same:

    (global-set-key (kbd "H-C-.") '(lambda () (interactive) (if (char-
equal (char-before) ?\s) (insert "->") (insert " ->")) (if (not (equal
(char-after) ?\s )) (insert " ") (forward-char))))
    (global-set-key (kbd "H-C-,") '(lambda () (interactive) (if (char-
equal (char-before) ?\s) (insert "<-") (insert " <-")) (if (not (equal
(char-after) ?\s )) (insert " ") (forward-char))))
    (global-set-key (kbd "H-C->") '(lambda () (interactive) (if (char-
equal (char-before) ?\s) (insert "=>") (insert " =>")) (if (not (equal
(char-after) ?\s )) (insert " ") (forward-char))))
    (global-set-key (kbd "H-C-<") '(lambda () (interactive) (if (char-
equal (char-before) ?\s) (insert "<=") (insert " <=")) (if (not (equal
(char-after) ?\s )) (insert " ") (forward-char))))

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ideasman_42 · 2022-08-02 12:02

You might want to exclude this when in strings/comments, (see
`(syntax-ppss)`), also, use \`save-match-data\` to avoid modifying
that, or better, use \`char-before\` since \`looking-back\` is slow.

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J-ky · 2022-08-02 12:57

Thank you so much. But I don't understand the `save-match-data` part,
how to use that?
```
(defun shapeless-c-arrow-insert-dot ()
  (interactive)
  (let ((sp (syntax-ppss)))
    (if (and (not (nth 4 sp))
             (not (nth 3 sp))
             (eq (char-before) ?\.))
        (progn
          (backward-delete-char 1)
          (insert "->"))
      (insert "."))))

```

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J-ky · 2022-08-02 12:59

What? Isn't a single '-' the minus sign in C?

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Phil-Hudson · 2022-08-02 15:58

Don't forget that `define-key` etc allow you to specify text to
insert. You don't have to call a command.

    (define-key c-mode "`" "->")

I chose `\`` because it's almost the only unshifted character (on a US
or UK keyboard) that isn't a C/C++ operator.

BTW, obviously `--` is not available in C/C++! It's one of the most
commonly used operators.

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Schievel1 · 2022-08-02 18:32

Yes, but it’s not like this is used everywhere. Like _ is in every
other variable name. Or {.
If you need a - and it would give you ->, you can just type backspace

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ideasman_42 · 2022-08-02 18:53

If you remove the `looking-at` / `looking-back` you don't need `save-
match-data`, otherwise you could do:

`(save-match-data (looking-back "."))`