Re^5: Recomendations For Learning perl?

Sure, here you go:

use strict; use warnings;
use Algorithm::Diff qw/ LCS_length /;

( my $name = $ARGV[0] ) && length $ARGV[0] > 2 or die "Usage: `$0 <nam
+e>` (min. 3 letters)";

open my $fh, '<', '/usr/share/dict/words' or die $!;

my $found = 0;
while ( <$fh> ) {
    next unless LCS_length( [ split //, $name ], [ split // ] ) == len
+gth $name;
    $found++;
    print "$found $_";
}

__END__
[download]

Things to maybe note:

How to load a clever module and import its LCS_length function to do all the work :-)
How to capture the user input from the command line in the array @ARGV
How to open a file for reading
How to create a counter and increment it in a loop
How to read from an open filehandle line-by-line (which avoids reading it all into memory), using:
```
while ( <$fh> ) {
    ...
}
[download]
```
The most obfuscated thing in this script: How to be lazy and not have to tell a function what to operate on by using the default argument, which is the current value of the magic variable $_. So in a loop I can say:
```
while ( <$fh> ) { # each line is loaded into $_ in turn
    my @characters = split //;
}
[download]
```
, omitting the second argument to split, and Perl knows to Do The Right Thing. More self-documenting usage would be:
```
while ( my $line = <$fh> ) { # each line now in $line
    my @characters = split //, $line;
}
[download]
```

Note that you can get documentation on many of Perl's built-in functions with perldoc -f <function_name>, e.g. perldoc -f split.

Hope this helps! have fun ....

edit: fixed missing parens

The way forward always starts with a minimal test.

Comment on Re^5: Recomendations For Learning perl? Select or Download Code

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Re^6: Recomendations For Learning perl? by adamZ88 (Beadle) on Dec 08, 2016 at 04:26 UTC
You are too kind! I totally do see myself thinking of a project like this one and making it a reality when I am more proficient in Perl. Surprisingly I follow almost all of your code! The two things that cause some head scratching is loading the module and the second argument that needs to be passed. Is this just the length of the name? I know I have loaded modules previously, I just forgot how, I will do my research.	[reply]
Re^7: Recomendations For Learning perl? by Laurent_R (Canon) on Dec 08, 2016 at 08:33 UTC
See Algorithm::Diff, especially the `LSC_length` function in http://search.cpan.org/~tyemq/Algorithm-Diff-1.1903/lib/Algorithm/Diff.pm#LCS_length. The program looks for your name's letters as subsequences of the words in the word list. If the length of the found subsequence is equal to the length of your name, then it means that all letters of your name were found in the right order in the candidate word.	[reply] [d/l]
Re^7: Recomendations For Learning perl? by 1nickt (Canon) on Dec 08, 2016 at 16:03 UTC
the second argument that needs to be passed. Is this just the length of the name? No, there's only one argument expected. That line of code is the program's error checking. It does two things, but acts on the same variable both times. ( my $name = $ARGV[0] ) && length $ARGV[0] > 2 or die "Usage: `$0 <nam +e>` (min. 3 letters)"; [download] What's happening here is we are evaluating the truth of an expression without using an explicit `if` statement. `my $name = $ARGV[0]` [download] will evaluate to false if the first argument passed in is empty (i.e. non-existent) because then the value of `$name` will be false (so `0` would fail also)`[1]`. If that happens, the `or die ...` kicks in. But if it evaluates to true, then `&& length $ARGV[0] > 2` [download] is evaluated for truth, so at this point we know we have some kind of value in the arg passed in, and now we check that it's at least three characters long. If the second part of the evaluation fails, the whole thing fails (because of the `&&`), and again we go to `or die ...`. Finally, in our error message emitted upon dying, we use `$0`, the global variable that holds the name of the currently executing script, and explain what the problem was. Amazing how much useful stuff you can do with one line of Perl, isn't it? `[1]` So in Perl you can evaluate truth very concisely: `while ( 1 ) { # runs forever ... } if ( 0 ) { # won't run ... } sub foo { return 'something'; # or maybe not } if ( foo() ) { # only runs if foo() returns something ... }` [download] Hope this helps. edit: added missing parens The way forward always starts with a minimal test.	[reply] [d/l] [select]
Re^8: Recomendations For Learning perl? by adamZ88 (Beadle) on Dec 08, 2016 at 20:18 UTC
Wow! I totally missed that. Yes, it is amazing how one line can achieve so much. Even as a beginner, I feel that I pressure myself to keep my code as concise as possible, thus, I like to achieve a lot with little code, though it does get confusing at times. Your breakdown of the program is very detailed and helpful! I was eager to try the program myself, so I installed the recommended module, copied the code and ran it. I did not have words installed, so I took care of that as well. The output is not as expected. I tried Steve's one-liner below and that works correctly for what it is supposed to do. But the output for your program is below: <Reveal this spoiler or all in this thread>	[reply] [d/l]
Re^9: Recomendations For Learning perl? -- be wise by Discipulus (Canon) on Dec 08, 2016 at 21:38 UTC
Re^10: Recomendations For Learning perl? -- be wise by adamZ88 (Beadle) on Dec 08, 2016 at 22:09 UTC
Re^9: Recomendations For Learning perl? by 1nickt (Canon) on Dec 08, 2016 at 21:10 UTC
Re^10: Recomendations For Learning perl? by adamZ88 (Beadle) on Dec 08, 2016 at 21:21 UTC
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