forward-paragraph, paragraph-start trouble

forward-paragraph, paragraph-start trouble

[John J Foerch]

Hello,

I am writing a major mode for a particular flavor of plain text file.  I
am having trouble coercing `forward-paragraph' to recognize the
paragraph style.  Here is some example text:

==begin example==

    This is the first paragraph.  It is
totally awesome.
    This is the second paragraph.  forward-paragraph
won't normally treat this one as a separate paragraph.

    But the real difficulty is when
    there is a paragraph like this.
    To find out whether a given line
    is a start-paragraph, you have
    to be able to look at the previous
    line to compare the amount of
    indentation.
        Crazy though it may seem,
    this sentence begins a new
    paragraph.

    This sentence, though formatted
    a bit strangely, should also be
treated as a single paragraph.

==end example==


`forward-paragraph' uses two regular expressions, `paragraph-start' and
`paragraph-separate' to find paragraphs.  I simply need to be able to
say that a line with more identation than the previous line is a
paragraph-start.  However, since emacs regular expressions lack
look-behind assertions, I am under the impression that what I want to do
is impossible.

Any advice?

Thank you,
John Foerch

Re: forward-paragraph, paragraph-start trouble

[Andreas Röhler]

Am Sonntag, 6. April 2008 01:20 schrieb John J Foerch:
>    line to compare the amount of
>     indentation.
>         Crazy though it may seem,
>     this sentence begins a new
>     paragraph.

What about this?

(defun my-paragraph-start (&optional indent this) 
  (interactive)
  (beginning-of-line)
  (or this (setq this (point-min)))
  (when (<= this (point)) 
    (let* ((pos (point)) 
	   (this-indent (- (progn (skip-chars-forward " \t")(point))pos))
	   (indent (or indent
		       this-indent)))
      (unless
	  (< indent this-indent)
	(forward-line 1)
	(my-paragraph-start this-indent (point))))))


Andreas Röhler

Re: forward-paragraph, paragraph-start trouble

[John J Foerch]

Andreas Röhler <andreas.roehler@online.de> writes:
> What about this?
>
> (defun my-paragraph-start (&optional indent this) 
>   (interactive)
>   (beginning-of-line)
>   (or this (setq this (point-min)))
>   (when (<= this (point)) 
>     (let* ((pos (point)) 
> 	   (this-indent (- (progn (skip-chars-forward " \t")(point))pos))
> 	   (indent (or indent
> 		       this-indent)))
>       (unless
> 	  (< indent this-indent)
> 	(forward-line 1)
> 	(my-paragraph-start this-indent (point))))))

Hi Andreas,

Thank you so much--I will play around with this code and see what I can
come up with.

Yet now I am thinking that the best course for me may be to modify
`forward-paragraph' perhaps to add a third regexp for finding paragraph
boundaries.  forward-paragraph is very dense code, and it may be a
considerable challenge to do what I want with it, but the advantage
would be that my mode would not have to have a complete set of its own
movement commands.  Presumably reducing code duplication is the
intention behind the variables `paragraph-start' and
`paragraph-separate', but unfortunately, they are not quite enough for
even this simple of a variation on emacs' standard paragraph style.

John Foerch