Re^2: How to make these reg exp changes?

$ perl -wle'
    my %neg = ( o => "i", i => "o" );

    while (<>) {
        chomp;
        s/([io])(M*)(\.+)/ $1.$2.( $neg{$1} x length($3) ) /eg;
        s/(\.+)(?=M*([io]))/ $neg{$2} x length($1) /eg;
        print;
    }
'
....MMMMiiii
....MMMMoooo
iiiiMMMM....
ooooMMMM....

ooooMMMMiiii
iiiiMMMMoooo
iiiiMMMMoooo
ooooMMMMiiii
[download]

Simpler version that only works with Perl 5.10+:

$ perl -wle'
    my %neg = ( o => "i", i => "o" );

    while (<>) {
        chomp;
        s/([io])M*\K(\.+)/   $neg{$1} x length($2) /eg;
        s/(\.+)(?=M*([io]))/ $neg{$2} x length($1) /eg;
        print;
    }
'
....MMMMiiii
....MMMMoooo
iiiiMMMM....
ooooMMMM....

ooooMMMMiiii
iiiiMMMMoooo
iiiiMMMMoooo
ooooMMMMiiii
[download]

I could have used -p above, but I wanted to make clear that %neg only needs to be initialized once without complicating the issue by adding a BEGIN. Here's the 5.10+ version using -p:

perl -ple'
    BEGIN { %neg = qw( i o o i ) }
    s/([io])M*\K(\.+)/   $neg{$1} x length($2) /eg;
    s/(\.+)(?=M*([io]))/ $neg{$2} x length($1) /eg;
'
[download]

Update: Added \K version. \K rocks.
Update: Added explanation about -p.

Comment on Re^2: How to make these reg exp changes? Select or Download Code

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Re^3: How to make these reg exp changes? by Anonymous Monk on Nov 16, 2009 at 00:09 UTC
exactly what I was looking for... The trick with the hash was just the thing! Thank you very much!	[reply]
Re^4: How to make these reg exp changes? by ikegami (Patriarch) on Nov 16, 2009 at 00:15 UTC
Honestly, the hash has nothing to do with the problem. `$neg{$1}` [download] is just short for `($1 eq 'o' ? 'i' : 'o')` [download]	[reply] [d/l] [select]
Re^4: How to make these reg exp changes? by Anonymous Monk on Nov 16, 2009 at 00:23 UTC
weird? `$s='III...MMMMMOOOO....MMMIIII'; print $s."\n"; %neg = ( O => "I", I => "O" ); $s=~s/([IO])(M)(\.+)/ $1.$2.( $neg{$1} x length($3) ) /eg; $s=~s/(\.+)(?=M([IO]))/ $neg{$2} x length($1) /eg; print $s;print "\n"; <code> It prints:<br> <code> III...MMMMMOOOO....MMMIIII IIIOOOMMMMMOOOOIIIIMMMIIII` [download]	[reply] [d/l]
Re^5: How to make these reg exp changes? by ikegami (Patriarch) on Nov 16, 2009 at 01:28 UTC
You told us that if the "." is not the first character, one should look back. Are you saying that's wrong? If you actually want to look to the other side of the adjacent Ms, `perl -wle' my %neg = ( O => "I", I => "O" ); $_ = "III...MMMMMOOOO....MMMIIII"; print; s/([IO])(M+)(\.+)/ $1.$2.( $neg{$1} x length($3) ) /eg; s/(\.+)(?=M+([IO]))/ $neg{$2} x length($1) /eg; print; '` [download]	[reply] [d/l]