Re: regex for a range that has a given number?

On 04/22/2010 03:37 PM, Peng Yu wrote:
>>> For exmaple, something like [7] [2-8] [2,4,8-10] in the
>>> maintext represent what articles that are listed in the
>>> bibliography are cited. Now, I want to search for where it
>>> cites citation number 7 in the maintext (in this example,
>>> it is cited the three places in the maintext).
>>
>> Or am I missing something. is 2-8 also valid for 7? If so, I
>> think you are out of luck for regex.
>
> 2-8 is also valid for 7.
>
> Is there anything that are more powerful than regex available
> in vim that can handle this case?

Not that I know of. To tackle the problem, I'd likely
create a search-function that looks for matches of the form

/\[\(\%(\d\+\%(-\d\+\)\=,\)*\%(\d\+\%(-\d\+\)\=\)]\)/

which should find all things that look like footnotes in
your text. Then split them on the comma, returning a list
of either pages or page-ranges, then if any of them have a
"-" in them, check if the target value is within that range,
otherwise just compare for equality. If you don't find any
match within the split-list, continue searching to the next
match of the above pattern. The pseduo-code (untested)
would look something like

function! FootSearch(fn)
let re='\[\(\%(\d\+\%(-\d\+\)\=,\)*\%(\d\+\%(-\d\+\)\=\)]\)'
let newmatch=searchpos(re, 's')
let initialmatch=newmatch
while newmatch != [0,0]
let [r,c]=newmatch
" m = the contents of the match
" with the "[" and "]" stripped off
" using the "[1:-2]"
let m=matchstr(getline(r)[c:], re)[1:-2]
for bit in split(m, ',')
" deal with any comma-separated list
" of pages or ranges
if bit=~'.*-.*'
" if it's a page-range
" pull the start/end
let [st, end]=split(bit, '-')
if st <= fn && fn <= end
" we're between the pages in that range
return
endif
else
if bit == fn
" it's an exact match
" might want do strip leading zeros
" from bit in case you search for "4"
" and the text contains [04]
return
endif
endif
endfor
" if we've not returned by now,
" this footnote doesn't match
" so find the next and keep going
let newmatch=searchpos(re, 's')
if newmatch == initialmatch
" we've found the first match again
" so we've likely looped around
" and we've not returned yet
" so prevent an infinite loop
break
endif
let [r,c]=newmatch
endwhile
endfunction

Any bugs are yours to keep ;-) But that's the general idea I'd use.

-tim

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