Programming

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Thu 9 Nov 2006

Choosing the Right Data Structure


Posted by Charles Clarkson under Perl, Programming
No Comments

The author of this module chose to use some file scoped variables in a module. This effectively created some global variables used outside the sub. This is not the recommended way to write a subroutine, but I needed an example and this one was handy. :)

PLAIN TEXT
PERL:
  1. my $htmltree;
  2. my $node;
  3. my @prevnodes;
  4. my $htmloutput;
  5.  
  6. sub start {
  7.     my $tagname = shift;
  8.     my $attr = shift;
  9.     my $newnode = {};
  10.  
  11.     $newnode->{tag} = $tagname;
  12.     foreach my $key(keys %{$attr}) {
  13.         $newnode->{$key} = $attr->{$key};
  14.     }
  15.     $newnode->{content} = [];
  16.     push @prevnodes, $node;
  17.     push @{$node}, $newnode;
  18.     $node = $newnode->{content};
  19. }

(more...)

 

Thu 9 Nov 2006

Simple File Opening in Perl


Posted by Charles Clarkson under Perl, Programming
No Comments

Opening files in perl is a fairly easy task. Here are the basic file opens. Do not use them in production code.

PLAIN TEXT
PERL:
  1. my $file = 'foo.txt';
  2.  
  3. # open for read
  4. open FH, ">$file";
  5.  
  6. # open for write
  7. open FH, ">$file";
  8.  
  9. # open for append
  10. open FH, ">>$file";

(more...)

 

Sat 28 Oct 2006

Read More, Type Less


Posted by Charles Clarkson under Perl, Programming
No Comments

There is an old saying amongst carpenters. Measure twice, cut once. This cuts down on materials. The same is true of typing for Perl programmers. Read more, type less. Okay, that doesn't have the same ring, but reading the documentation before writing your script does make sense.

I came across a script recently where a beginner programmer had obviously decided that typing was easier than reading. Here's an excerpt. The author needs to start a really wide table, but won't end it for a while yet.

PLAIN TEXT
PERL:
  1. use CGI qw/:standard/;
  2.  
  3. print "<table border = 1>",th,"day",td,"Date",td,"Time In",td,"Break Start",td,"Break End",td,"Time Out",td,"Evening In",td,"Evening Out",td,"flex hours",td,"flex bal",td,"lieu",td,"adjustment",td,"lieu adjustment",td,"type";

(more...)

 

Mon 23 Oct 2006

A VBA Solution


Posted by Charles Clarkson under Programming, Visual Basic
No Comments

 

Thu 7 Sep 2006

DWIM and DWIW


Posted by Charles Clarkson under Perl, Programming
No Comments

Many times when writing code, a beginner will ask the language to perform an operation and receive an unusual result. While possible, it is highly unlikely that a beginner will find a bug in perl, JavaScript, etc. Programmers must be humble. The fault ususally lies with us.

Chances are we are asking the programming language to do what we mean instead of telling it what we really want to do. Some languages have logic builin that will try to guess when something might go either way, but we shouldn't depend on this.

Here's an example

PLAIN TEXT
PERL:
  1. $time = "10:10:00";
  2. $other_time = "10:10:40";
  3. print $time - $other_time;

No web programming language will return 40 seconds as the answer without extra work.

The programming language does what I want (DWIW), when I was hoping it would do what I mean (DWIM). The next time you don't get a desired result, make certain you are using DWIW.

 

Wed 6 Sep 2006

Looking Under the Hood


Posted by Charles Clarkson under Perl, Programming
No Comments

Sometimes you just have to peek. Whether it's baking brownies, an overheated engine, or a data structure, sometimes you just have to look under the hood. When programming in perl you need to dump the contents of your data structure to see what's there.

PLAIN TEXT
PERL:
  1. #!/usr/bin/perl
  2.  
  3. use strict;
  4. use warnings;
  5. use Data::Dumper 'Dumper';
  6.  
  7. my @sirsi_array = (
  8.     '671|Psychophysiology|PPSY',
  9.     '671|Psychophysiology|http://www.blackwell-synergy.com/servlet/useragent?func=showIssues&code=psyp',
  10.     '675|Notes and queries|PENG',
  11.     '675|Notes and queries|http://www.bodley.ox.ac.uk/ilej/journals',
  12.     '675|Notes and queries|http://www.ingenta.com/journals/browse/oup/notesj',
  13.     '676|The Journal of general psychology|http://asa.lib.lehigh.edu/cgi-bin/pubid?Pub=14345',
  14.     '681|Greece & Rome|PHIS',
  15.     '681|Greece & Rome|http://www.jstor.org/journals/00173835.html',
  16.     '681|Greece & Rome|http://www3.oup.co.uk/gromej/contents.html',
  17. );
  18.  
  19. my %sirsi;
  20. foreach my $item ( @sirsi_array ) {
  21.     my( $key, $title, $data ) = split /|/, $item;
  22.     push @{ $sirsi{ $key } }, [ $key, $title, ];
  23. }
  24.  
  25. print Dumper \%sirsi;
  26.  
  27. __END__

(more...)

 

Tue 5 Sep 2006

Code Organization


Posted by Charles Clarkson under Perl, Programming
No Comments

This may seem trivial, but I believe how we organize programs is directly influenced by how we think. Perhaps learning to better organize code will lead to better organized, more efficient thinking.

PLAIN TEXT
PERL:
  1. #!/usr/local/bin/perl -w
  2. use strict;
  3. open (FH,"/usr/local/bin/perld/derektapes") or die "cannot open FH: $!\n";
  4. my $w_param="-w ";
  5. my $tick="'";
  6. my $b_param="barcode=";
  7. my $or_string=" or ";
  8. chomp ( my @a = <FH>);
  9.  
  10. #       $a[$i]=$_;
  11. #       $i++;
  12. #       print map {$_, "\n"} @a;
  13.  
  14.         print $w_param,  $tick;
  15.         while (@a) {
  16.         my @output = ();
  17.                 for ( 1..4 ) {
  18.                         push @output, $b_param . shift @a;
  19.                         last unless @a;
  20.                 }
  21.         print join ($or_string, @output),"\n";
  22.         }
  23. print $tick;

(more...)

 

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