Re^2: combining lists along with a regex

That's got it Athanasius, thank you. Once you explained what I was doing and showed the folly of capturing what I didn't need, it all came together.

0. Amber B. was harmed by J.
1. Kim B. was harmed by B F K.
2. Kim W. was harmed by A I J.
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The regexes are much tidier now. I still think I need to strip off whitespace on the RHS. I suppose I could try to roll it all into one if I get ambitious, but I think it adds legibility to make it a different step:

  for (@name) {
    s/\s+$//;
    my $int = s/^(\d+\.\s+\w+\s+\w).*$/$1\. /;
    say "int is $int"; 
  }
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  for  (@harm) {
    s/\s+$//;
    my $int = s/^\d+\.\s+(\w.*)$/was harmed by $1\./;
    say "schmint is $int";
  }
[download]

This will do nicely for now, but I'm open to any other opinions.

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Re^3: combining lists along with a regex
by Athanasius (Archbishop) on May 09, 2015 at 08:19 UTC

I think it adds legibility to make it a different step

I totally agree, in the general case. In this specific case, however, the first substitution — explicitly stripping off trailing whitespace — is in fact not needed at all, because the second substitution does that anyway:

18:14 >perl -wE "my $s = '2. Kim Washington      '; $s =~ s/^\d+\.\s+(
+\w+\s+\w).*$/$1. /; say qq['$s'];"
'Kim W. '

18:14 >
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Note also that in a substitution, only the left-hand part is a regex; the right-hand part is just an (interpolated) string, so the . doesn’t need to be escaped.

Hope that helps,

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

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Re^4: combining lists along with a regex

by Aldebaran (Curate) on May 10, 2015 at 01:37 UTC

Hmmm. Not meaning to quibble, but I notice your inputs don't have the newlines that mine do, which I don't want in the output, as I want to provide my own as opposed to reproducing whatever I had in the input, which may or may not be a windows-appropriate list, as that is where these get printed off ultimately. I've read (in perlmonks) that s/\s+$//; is the best way to strip newlines and extra spacing on RHS. Without them I get this:

0. Amber B. 
was harmed by J.

1. Kim B. 
was harmed by B F K.

2. Kim W. 
was harmed by A I J.
[download]

Now that I look at this, it isn't at all clear to me how I would accomplish that in one step with the greediness of the .*. Indeed, I don't understand why it doesn't match .* and get discarded without the s/\s+$//;:

 
  for (@name) {
    s/\s+$//;
    my $int = s/^(\d+\.\s+\w+\s+\w).*$/$1. /;
    say "int is $int"; 
  }
  for  (@harm) {
    s/\s+$//;
    my $int = s/^\d+\.\s+(\w.*)$/was harmed by $1./;
    say "schmint is $int";
  }
[download]

0. Amber B. was harmed by J.
1. Kim B. was harmed by B F K.
2. Kim W. was harmed by A I J.
[download]

The point about the period not needing to be escaped in the right hand part of the substitution is well-taken and reflected in the above. Thanks again.

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Re^5: combining lists along with a regex

by Athanasius (Archbishop) on May 10, 2015 at 02:54 UTC

You’re right, I didn’t take newlines into account. You could always chomp the line before the substitution. However, to do it all in one step, you need to add an /s modifier to the (regex part of the) substitution:

12:51 >perl -wE "my $s = qq[Hello world.  \n]; $s =~ s/^.*(world).*$/m
+onks/; say qq[|$s|];"
|monks
|

12:51 >perl -wE "my $s = qq[Hello world.  \n]; $s =~ s/^.*(world).*$/m
+onks/s; say qq[|$s|];"
|monks|

12:51 >
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See perlre#Modifiers.

Hope that helps,

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

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