Re: Extended glob patterns in ${...#..} RE: Un-patch: new pattern matching code

["Bart Schaefer" <schaefer@candle.brasslantern.com>]

On Aug 9, 10:25am, Andrej Borsenkow wrote:
} Subject: RE: Extended glob patterns in ${...#..} RE: Un-patch: new pattern
}
} > Since a closure can match the empty string, the shortest matched portion
} > is nothing.  However, asking for the longest match definitely doesn't work:
} >
} > zagzig<9> print ${(SM)foo##*}
} > ab12xy
} > zagzig<10> print ${(SM)foo##([[:digit:]])#}
} >
} > zagzig<11>
} 
} Believe it or not, it does work today. I have no idea, what went wrong
} yesterday (I thought, it was the problem of flag order ...):

I think it's the difference between .6 and .6-pws-1 (I find myself wishing
Peter had chosen a different suffix this time; it's going to be confusing
especially during archive searches to decide which base version is meant
when someone refers to psw-N).

} But still, this one is probably unexpected:
} 
} bor@itsrm2:~%> print ${(MSI:2:)foo##[[:digit:]]#}
} 2
} 
} The first is O.K. ... and the third is O.K., but the second? I believe,
} this is a clear bug. The ``S'' flag must consider only non-overlapped
} matches (the same way, sed works).

The (S) flag has recognized overlapping matches for as long as it exsisted.
Remember, it means on "match within a substring" (it effectively turns
off the implicit start-anchor of # or end-anchor of %).

I think what you mean is that the (I::) flag should skip the overlapping
matches.  I suppose it could be proclaimed a bug fix, but consider the
example below -- don't you WANT overlapping matches in that instance?

I don't know how heavily the (I::) flag is employed by 3.0.x users, but
some differences have already been introduced; with x="a1_b_a2_c_a3_d" the
two look like:
====================================+========================================
zsh-3.0.6: print ${(MS)x##a*}       | zsh-3.1.6-pws-1: print ${(MS)x##a*}
a1_b_a2_c_a3_d                      | a1_b_a2_c_a3_d
zsh-3.0.6: print ${(MSI:2:)x##a*}   | zsh-3.1.6-pws-1: print ${(MSI:2:)x##a*}
a1_b_a2_c_a3_                       | a2_c_a3_d
zsh-3.0.6: print ${(MSI:3:)x##a*}   | zsh-3.1.6-pws-1: print ${(MSI:3:)x##a*}
a1_b_a2_c_a3                        | a3_d
zsh-3.0.6: print ${(MSI:4:)x##a*}   | zsh-3.1.6-pws-1: print ${(MSI:4:)x##a*}
a1_b_a2_c_a                         | 
zsh-3.0.6: print ${(SMI:5:)x##a*}   | zsh-3.1.6-pws-1: print ${(SMI:5:)x##a*}
a1_b_a2_c                           | 
====================================+========================================

Note that 3.0.6 is using overlapping matches and counting from the longest
to the shortest starting at the right, whereas 3.1.6-pws-1 is counting from
the left (which I admit is more intuitive, but it is skipping a lot of
possible matches that way without skipping all of them).  3.0.6 rambles on:

1 = a1_b_a2_c_a3_d
2 = a1_b_a2_c_a3_
3 = a1_b_a2_c_a3
4 = a1_b_a2_c_a
5 = a1_b_a2_c_
6 = a1_b_a2_c
7 = a2_c_a3_d
8 = a1_b_a2_
9 = a2_c_a3_
10 = a1_b_a2
11 = a2_c_a3
12 = a1_b_a
13 = a2_c_a
14 = a1_b_
15 = a2_c_
16 = a1_b
17 = a2_c
18 = a3_d
19 = a1_
20 = a2_
21 = a3_
22 = a1
23 = a2
24 = a3
25 = a
26 = a
27 = a

This is a pretty significant difference in behavior.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com