Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Implement backward case in haskell-forward-sexp #1158

Merged
merged 1 commit into from
Feb 16, 2016
Merged

Implement backward case in haskell-forward-sexp #1158

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 19 additions & 7 deletions haskell-mode.el
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -849,16 +849,28 @@ it that many times. Negative arg -N means move backward across N
balanced expressions. This command assumes point is not in a
string or comment.

Note that negative arguments do not work so well."
If unable to move over a sexp, signal `scan-error' with three
arguments: a message, the start of the obstacle (a parenthesis or
list marker of some kind), and end of the obstacle."
(interactive "^p")
(or arg (setq arg 1))
(if (< arg 0)
;; Fall back to native Emacs method for negative arguments.
;; Haskell has maximum munch rule that does not work well
;; backwards.
(progn
(goto-char (or (scan-sexps (point) arg) (buffer-end arg)))
(backward-prefix-chars))
(while (< arg 0)
(skip-syntax-backward "->")
;; Navigate backwards using plain `backward-sexp', assume that it
;; skipped over at least one Haskell expression, and jump forward until
;; last possible point before the starting position. If applicable,
;; `scan-error' is signalled by `backward-sexp'.
(let ((end (point))
(forward-sexp-function nil))
(backward-sexp)
(let ((cur (point)))
(while (< (point) end)
(setf cur (point))
(haskell-forward-sexp)
(skip-syntax-forward "->"))
(goto-char cur)))
(setf arg (1+ arg)))
(save-match-data
(while (> arg 0)
(when (haskell-lexeme-looking-at-token)
Expand Down
21 changes: 21 additions & 0 deletions tests/haskell-mode-tests.el
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -464,4 +464,25 @@ of sexp."
(haskell-forward-sexp 1)
(eq (point) 6))))

(ert-deftest backward-sexp ()
"Check if `forward-sexp-function' behaves properly on
beginning of sexp."
(should (with-temp-buffer
(haskell-mode)
(insert "(foo) bar")
(goto-char 2)
(condition-case err
(progn (backward-sexp)
nil)
(scan-error (equal (cddr err) (list 1 1)))))))

(ert-deftest haskell-backward-sexp ()
"Check if `haskell-forward-sexp' with negatives arg properly
moves over sexps."
(should (with-temp-buffer
(insert "a (b c) = d . e")
(goto-char 15)
(haskell-forward-sexp -4)
(eq (point) 3))))

(provide 'haskell-mode-tests)