On Thursday, April 5, 2012 10:13:55 PM UTC-5, John Little wrote:
> On Friday, April 6, 2012 10:02:48 AM UTC+12, Ben Fritz wrote:
> > Please give the EXACT command you ran...
> 
> Perhaps this script will illustrate:
> 
>     let s = '-2 3-4-5-6-7-8'
>     let p = '\([0-9-]\@<!-\)\?\d[0-9]*'
>     let [start, end] = [0, 0]
>     while 1
>         let start = match(s, p, end)
>         let end   = matchend(s, p, end)
>         if start == -1
>             break
>         endif
>         echo s[start : end-1]
>     endwhile
> 
> I get:
> 
>     -2
>     3
>     -4
>     -5
>     -6
>     -7
>     -8
> 
> It would appear that using the third parameter to match() and matchend(), the 
> match is done as if on a substring starting at the parameter, so the look 
> behind assertion does not see what's there in the original string.
> 
> This is unlike searching in a buffer; the look behind assertion does look 
> behind the start position of the search. Rameo, is this what you're getting 
> at?
> 

I think you've analyzed it perfectly! Looking closer at the help for match(), I 
see:

                For a String, if {start} > 0 then it is like the string starts
                {start} bytes later, thus "^" will match at {start}.  Except
                when {count} is given, then it's like matches before the
                {start} byte are ignored

So with only 3 arguments, from this help text, I would expect exactly the 
results given, for the reason given.

However, this gave me a hint to fix the problem. With a minor tweak:

   let s = '-2 3-4-5-6-7-8'
    let p = '\([0-9-]\@<!-\)\?\d[0-9]*'
    let [start, end] = [0, 0]
    while 1
        " count=1 to ignore previous matches rather than making the string
        " start at a new place
        let start = match(s, p, end, 1)
        let end   = matchend(s, p, end, 1)
        if start == -1
            break
        endif
        echo s[start : end-1]
    endwhile

It works as intended. With this script, I get:

-2
3
4
5
6
7
8

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