📄 pattern matching.mht

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color=3D#b2dfee>is_valid_pattern</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ffa500>my</FONT> <FONT color=3D#9ac0cd>$pat</FONT> =
=3D <FONT color=3D#ff7f50>shift</FONT><FONT color=3D#00ffff>;</FONT>
    <FONT color=3D#ffa500>return</FONT> <FONT =
color=3D#ffa500>eval</FONT> <FONT color=3D#00ffff>{</FONT> <FONT =
color=3D#00cd00>""</FONT> =3D~ /$pat/<FONT color=3D#00ffff>;</FONT> =
<FONT color=3D#cdcd00>1</FONT> <FONT color=3D#00ffff>}</FONT> || <FONT =
color=3D#cdcd00>0</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
# <FONT size=3D-1><A =
href=3D"http://pleac.sourceforge.net/include/perl/ch06/paragrep">download=
 the following standalone program</A></FONT>
#!/usr/bin/perl
# paragrep - trivial paragraph grepper
</FONT><FONT color=3D#ffa500>die</FONT> <FONT color=3D#00cd00>"usage: $0 =
pat [files]\n"</FONT> <FONT color=3D#ffa500>unless</FONT> <FONT =
color=3D#cdad00>@ARGV</FONT><FONT color=3D#00ffff>;</FONT>
$/ =3D <FONT color=3D#00cd00>''</FONT><FONT color=3D#00ffff>;</FONT>
$pat =3D <FONT color=3D#ff7f50>shift</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#ffa500>eval</FONT> <FONT color=3D#00ffff>{</FONT> <FONT =
color=3D#00cd00>""</FONT> =3D~ /$pat/<FONT color=3D#00ffff>;</FONT> =
<FONT color=3D#cdcd00>1</FONT> <FONT color=3D#00ffff>}</FONT>      <FONT =
color=3D#98fb98>or</FONT> <FONT color=3D#ffa500>die</FONT> <FONT =
color=3D#00cd00>"$0: Bad pattern $pat: $@\n"</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#ffa500>while</FONT> <FONT =
color=3D#00ffff>(</FONT>&lt;&gt;<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"$ARGV $.: =
$_"</FONT> <FONT color=3D#ffa500>if</FONT> /$pat/o<FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>

<FONT color=3D#bebebe>#-----------------------------
</FONT>$pat =3D <FONT color=3D#00cd00>"You lose @{[ system('rm -rf *')]} =
big here"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$safe_pat =3D <FONT color=3D#98fb98>quotemeta</FONT><FONT =
color=3D#00ffff>(</FONT>$pat<FONT color=3D#00ffff>);</FONT>
something<FONT color=3D#00ffff>()</FONT> <FONT color=3D#ffa500>if</FONT> =
/$safe_pat/<FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>something<FONT color=3D#00ffff>()</FONT> <FONT =
color=3D#ffa500>if</FONT> /\Q$pat/<FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN321>Honoring Locale Settings in Regular=20
Expressions</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>use</FONT> <FONT =
color=3D#b2dfee>locale</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
# <FONT size=3D-1><A =
href=3D"http://pleac.sourceforge.net/include/perl/ch06/localeg">download =
the following standalone program</A></FONT>
#!/usr/bin/perl -w
# localeg - demonstrate locale effects
</FONT>
<FONT color=3D#ffa500>use</FONT> <FONT =
color=3D#b2dfee>locale</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ffa500>use</FONT> <FONT color=3D#b2dfee>POSIX</FONT> =
<FONT color=3D#00cd00>'locale_h'</FONT><FONT color=3D#00ffff>;</FONT>

$name =3D <FONT color=3D#00cd00>"andreas k\xF6nig"</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#cdcd00>@locale</FONT><FONT color=3D#00ffff>{</FONT><FONT =
color=3D#ff7f50>qw</FONT><FONT color=3D#00ffff>(</FONT>German =
English<FONT color=3D#00ffff>)}</FONT> =3D <FONT =
color=3D#ff7f50>qw</FONT><FONT color=3D#00ffff>(</FONT>de_DE.ISO_<FONT =
color=3D#cdcd00>8859-1</FONT> us-ascii<FONT color=3D#00ffff>);</FONT>
setlocale<FONT color=3D#00ffff>(</FONT>LC_CTYPE, <FONT =
color=3D#cdcd00>$locale</FONT><FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>English</FONT><FONT color=3D#00ffff>})</FONT>
  <FONT color=3D#98fb98>or</FONT> <FONT color=3D#ffa500>die</FONT> <FONT =
color=3D#00cd00>"Invalid locale </FONT><FONT =
color=3D#cdcd00>$locale</FONT><FONT =
color=3D#00cd00>{English}"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#cdad00>@english_names</FONT> =3D <FONT =
color=3D#00ffff>();</FONT>
<FONT color=3D#ffa500>while</FONT> <FONT color=3D#00ffff>(</FONT>$name =
=3D~ /\b<FONT color=3D#00ffff>(</FONT>\w+<FONT =
color=3D#00ffff>)</FONT>\b/g<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
        <FONT color=3D#ff7f50>push</FONT><FONT =
color=3D#00ffff>(</FONT><FONT color=3D#cdad00>@english_names</FONT>, =
<FONT color=3D#98fb98>ucfirst</FONT><FONT color=3D#00ffff>(</FONT>$<FONT =
color=3D#cdcd00>1</FONT><FONT color=3D#00ffff>));</FONT>
<FONT color=3D#00ffff>}</FONT>
setlocale<FONT color=3D#00ffff>(</FONT>LC_CTYPE, <FONT =
color=3D#cdcd00>$locale</FONT><FONT color=3D#00ffff>{</FONT><FONT =
color=3D#00cd00>German</FONT><FONT color=3D#00ffff>})</FONT>
  <FONT color=3D#98fb98>or</FONT> <FONT color=3D#ffa500>die</FONT> <FONT =
color=3D#00cd00>"Invalid locale </FONT><FONT =
color=3D#cdcd00>$locale</FONT><FONT =
color=3D#00cd00>{German}"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#cdad00>@german_names</FONT> =3D <FONT =
color=3D#00ffff>();</FONT>
<FONT color=3D#ffa500>while</FONT> <FONT color=3D#00ffff>(</FONT>$name =
=3D~ /\b<FONT color=3D#00ffff>(</FONT>\w+<FONT =
color=3D#00ffff>)</FONT>\b/g<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
        <FONT color=3D#ff7f50>push</FONT><FONT =
color=3D#00ffff>(</FONT><FONT color=3D#cdad00>@german_names</FONT>, =
<FONT color=3D#98fb98>ucfirst</FONT><FONT color=3D#00ffff>(</FONT>$<FONT =
color=3D#cdcd00>1</FONT><FONT color=3D#00ffff>));</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"English names: =
</FONT><FONT color=3D#cdad00>@english_names</FONT><FONT =
color=3D#00cd00>\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"German names:  =
</FONT><FONT color=3D#cdad00>@german_names</FONT><FONT =
color=3D#00cd00>\n"</FONT><FONT color=3D#00ffff>;</FONT>

English names: Andreas K Nig

German names:  Andreas K=F6nig
<FONT color=3D#bebebe>#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN324>Approximate Matching</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>use</FONT> <FONT =
color=3D#b2dfee>String::Approx</FONT> <FONT =
color=3D#ff7f50>qw</FONT><FONT color=3D#00ffff>(</FONT>amatch<FONT =
color=3D#00ffff>);</FONT>

<FONT color=3D#ffa500>if</FONT> <FONT =
color=3D#00ffff>(</FONT>amatch<FONT color=3D#00ffff>(</FONT><FONT =
color=3D#00cd00>"PATTERN"</FONT>, <FONT =
color=3D#cdad00>@list</FONT><FONT color=3D#00ffff>))</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#bebebe># matched
</FONT><FONT color=3D#00ffff>}</FONT>

<FONT color=3D#cdad00>@matches</FONT> =3D amatch<FONT =
color=3D#00ffff>(</FONT><FONT color=3D#00cd00>"PATTERN"</FONT>, <FONT =
color=3D#cdad00>@list</FONT><FONT color=3D#00ffff>);</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>use</FONT> <FONT =
color=3D#b2dfee>String::Approx</FONT> <FONT =
color=3D#ff7f50>qw</FONT><FONT color=3D#00ffff>(</FONT>amatch<FONT =
color=3D#00ffff>);</FONT>
<FONT color=3D#98fb98>open</FONT><FONT color=3D#00ffff>(</FONT>DICT, =
<FONT color=3D#00cd00>"/usr/dict/words"</FONT><FONT =
color=3D#00ffff>)</FONT>               <FONT color=3D#98fb98>or</FONT> =
<FONT color=3D#ffa500>die</FONT> <FONT color=3D#00cd00>"Can't open dict: =
$!"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ffa500>while</FONT><FONT =
color=3D#00ffff>(</FONT>&lt;DICT&gt;<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#ffa500>if</FONT> =
amatch<FONT color=3D#00ffff>(</FONT><FONT =
color=3D#00cd00>"balast"</FONT><FONT color=3D#00ffff>);</FONT>
<FONT color=3D#00ffff>}</FONT>

ballast

balustrade

blast

blastula

sandblast
<FONT color=3D#bebebe>#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN327>Matching from Where the Last Pattern =
Left=20
Off</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>while</FONT> <FONT =
color=3D#00ffff>(</FONT>/<FONT color=3D#00ffff>(</FONT>\d+<FONT =
color=3D#00ffff>)</FONT>/g<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"Found =
$1\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$n =3D <FONT color=3D#00cd00>"   49 here"</FONT><FONT =
color=3D#00ffff>;</FONT>
$n =3D~ <FONT color=3D#ff7f50>s</FONT>/\G /<FONT =
color=3D#cdcd00>0</FONT>/g<FONT color=3D#00ffff>;</FONT>
<FONT color=3D#ff7f50>print</FONT> $n<FONT color=3D#00ffff>;</FONT>
<FONT color=3D#cdcd00>00049</FONT> here
<FONT color=3D#bebebe>#-----------------------------
</FONT><FONT color=3D#ffa500>while</FONT> <FONT =
color=3D#00ffff>(</FONT>/\G,?<FONT color=3D#00ffff>(</FONT>\d+<FONT =
color=3D#00ffff>)</FONT>/g<FONT color=3D#00ffff>)</FONT> <FONT =
color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"Found =
number $1\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT>$_ =3D <FONT color=3D#00cd00>"The year 1752 lost 10 days on the =
3rd of September"</FONT><FONT color=3D#00ffff>;</FONT>

<FONT color=3D#ffa500>while</FONT> <FONT color=3D#00ffff>(</FONT>/<FONT =
color=3D#00ffff>(</FONT>\d+<FONT color=3D#00ffff>)</FONT>/gc<FONT =
color=3D#00ffff>)</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"Found =
number $1\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>

<FONT color=3D#ffa500>if</FONT> <FONT color=3D#00ffff>(</FONT>/\G<FONT =
color=3D#00ffff>(</FONT>\S+<FONT color=3D#00ffff>)</FONT>/g<FONT =
color=3D#00ffff>)</FONT> <FONT color=3D#00ffff>{</FONT>
    <FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"Found $1 =
after the last number.\n"</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#00ffff>}</FONT>

<FONT color=3D#bebebe>#Found number 1752
#
#Found number 10
#
#Found number 3
#
#Found rd after the last number.
#-----------------------------
</FONT><FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"The =
position in \$a is "</FONT>, <FONT color=3D#ff7f50>pos</FONT><FONT =
color=3D#00ffff>(</FONT>$a<FONT color=3D#00ffff>);</FONT>
<FONT color=3D#ff7f50>pos</FONT><FONT color=3D#00ffff>(</FONT>$a<FONT =
color=3D#00ffff>)</FONT> =3D <FONT color=3D#cdcd00>30</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#ff7f50>print</FONT> <FONT color=3D#00cd00>"The position =
in \$_ is "</FONT>, <FONT color=3D#ff7f50>pos</FONT><FONT =
color=3D#00ffff>;</FONT>
<FONT color=3D#ff7f50>pos</FONT> =3D <FONT =
color=3D#cdcd00>30</FONT><FONT color=3D#00ffff>;</FONT>
<FONT color=3D#bebebe>#-----------------------------
</FONT></PRE></FONT></TD></TR></TBODY></TABLE></DIV>
<DIV class=3DSECT2>
<H2 class=3DSECT2><A name=3DAEN330>Greedy and Non-Greedy =
Matches</A></H2>
<TABLE width=3D"100%" bgColor=3D#2f4f4f border=3D0>
  <TBODY>
  <TR>
    <TD><PRE class=3DSCREEN><FONT color=3D#f5deb3 size=3D+1><FONT =
color=3D#bebebe>#-----------------------------
# greedy pattern
</FONT><FONT color=3D#ff7f50>s</FONT>/&lt;.*&gt;//gs<FONT =
color=3D#00ffff>;</FONT>                     <FONT color=3D#bebebe># try =
to remove tags, very badly
</FONT>
<FONT color=3D#bebebe># non-greedy pattern
</FONT><FONT color=3D#ff7f50>s</FONT>/&lt;.*?&gt;//gs<FONT =
color=3D#00ffff>;</FONT>                    <FONT color=3D#bebebe># try =
to remove tags, still rather badly
#-----------------------------
#&
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