f77coder has asked for the wisdom of the Perl Monks concerning the following question:

hello, i've been hacking away at this but can't get the correct regex expression and would like a little help.

old C-style macros in headers files are #ifdef __some_Long_name__ which start and end with double underlines and look like perl literals

in C++14, i'd like to batch convert these macros to standard which strips the double underscores and convert strings to upper case like this

SOME_LONG_NAME

i like one-liners, so i've tried these and many variations to escaping the underscores 

perl -pi -e 's/__*__/\uc($1)/g' a.test;
perl -pi -e 's/__*__/\U$1/g' a.test

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thanks
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Re: another string replacement with uppercase :: converting C macros to C++
by Athanasius (Cardinal) on Jan 23, 2016 at 08:30 UTC

    Hello f77coder,

    Your first try is close, but has two problems:

    1. You need to capture the text between the double underlines
    2. To run a perl function in the replacement part of a substitution, you need to add an /e modifier.
    #! perl
use strict;
use warnings;

while (<DATA>)
{
    s/__(\S+?)__/uc($1)/eg;
    print;
}

__DATA__
#ifdef __some_Long_name__
do stuff
#endif

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    Output:

    18:25 >perl 1523_SoPW.pl
#ifdef SOME_LONG_NAME
do stuff
#endif

18:27 >

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    Hope that helps,

    Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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      For uppercasing, of course, there is also the builtin \U. 
      s/\b__(\w+)__\b/\U$1/;

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        Good point! I’d forgotten about these (if I ever knew them1) — except for \Q, which I often have to use. For the record, they’re documented here:

        19:11 >perl -wE "my $s = qq[abc\Udef\Eghijk]; say $s;"
abcDEFghijk

19:13 >

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        Good to know, thanks!

        Update: 1I must have read about them any number of times. But unfortunately it seems that reading about ≠ knowing, unless it’s combined with using. ;-)

        Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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      The second is not farther: 
      s/__(\S+)__/\U$1/g

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      ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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      Excellent! Works like a charm

      Thanks you very much.

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Re: another string replacement with uppercase :: converting C macros to C++
by AnomalousMonk (Archbishop) on Jan 23, 2016 at 18:09 UTC

    Beware the wily corner case. I don't know if  '#ifdef ___xxx___' and the cases that follow it are pertinent to your application, but just something to think about: 

    c:\@Work\Perl\monks>perl -wMstrict -le
"my @ln = (
   '#ifdef __some__Long_name__',
   '__w_x__y_z__',
   '__aa_bb__cc___dd__ xxx __pp__qq__',
   '#ifdef ___xxx___',
   '#ifdef __xxx',
   '#ifdef xxx__',
   );
 ;;
 for my $s (@ln) {
   print qq{'$s'};
   $s =~ s{ \b __ (\w+?) __ \b }{\U$1}xmsg;
   print qq{'$s' \n};
   }
"
'#ifdef __some__Long_name__'
'#ifdef SOME__LONG_NAME'

'__w_x__y_z__'
'W_X__Y_Z'

'__aa_bb__cc___dd__ xxx __pp__qq__'
'AA_BB__CC___DD xxx PP__QQ'

'#ifdef ___xxx___'
'#ifdef _XXX_'

'#ifdef __xxx'
'#ifdef __xxx'

'#ifdef xxx__'
'#ifdef xxx__'

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    Give a man a fish:  <%-{-{-{-<

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