[NTG-context] regexp for matching entire footnotes

Hans Hagen pragma at wxs.nl
Sun Jul 30 21:28:44 CEST 2006

Sanjoy Mahajan wrote:
>> I have to find (highlight) footnotes with the entire footnote being
>> marked/highlighted.  The problems are the (potentially) nested pairs
>> of curled brackets (like for \index, \emphasize etc etc) ...
> I'm not sure what you mean by marking or highlighting the footnote.
> Do you mean in the printed document, or in the source file so that you
> can find and change them in some way?
>> Constructing a regexp for this is far beyond what I can write,
> In the Chomsky hierarchy of grammars, regular languages, which are
> recognized by regexps, are below context-free grammars (CFGs).
> Compared to regular languages, CFGs add a stack.  And you need a stack
> to parse nested delimiters, otherwise you can't tell whether a closing
> brace closes the first opening brace.  So no regexp can do what you
> hope for.
lua reg exps have a way do handle nested () {} []
> You could:
> 1. Use emacs (or your favorite editor) to substitute \myfootnote for
>    \footnote, and do some ConTeXt setup magic to make \myfootnote be
>    just like \footnote except that it highlights.
> 2. Use Emacs, which can find balanced braces, to make a keyboard macro
>    (start defining it with "C-x (").  Then:
>    a. search for \footnote.  Now the point will be between the 'e'
>       and the opening '{'.
>    b. C-@ to set the mark.
>    c. C-M-f ("alt-ctrl-f" to run 'forward-sexp') to move to the
>       closing brace.  Now you'll have highlighted the {...} stuff of
>       the \footnote.
>    d. C-x ) to end the keyboard macro definition.
>    Then you can use C-x e to go to and highlight the next footnote
>    material.
> But I'm not sure either is what you're trying to do?
a multistep approach is possible: 

- mark each { } with something that reflects nesting (say <{1> <{2> <}2>    <}1> etc
- you can now distinguish matching pairs and take some action
- afterwards you convert the <..> things back to { } 

(at least that is how i did such thing until now in e.g. ruby) 


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