Day 16: Script Development Suggested Reading: The Story of Mel - PowerPoint PPT Presentation

Computer Sciences 368 Introduction to Perl Day 16: Script Development Suggested Reading: The Story of Mel (slide 5) A good book (not about Perl) 2012 Summer Cartwright 1

Computer Sciences 368 Introduction to Perl Homework Review 2012 Summer Cartwright 2

Computer Sciences 368 Introduction to Perl Priorities 2012 Summer Cartwright 3

Computer Sciences 368 Introduction to Perl E ffi ciency Correctness Clarity 2012 Summer Cartwright 4

Computer Sciences 368 Introduction to Perl The Story of Mel http://rixstep.com/2/2/20071015,01.shtml 2012 Summer Cartwright 5

Computer Sciences 368 Introduction to Perl E ffi cient (?) but Unclear opendir $dir_fh, $cwd; my @dir_stack = readdir $dir_fh; @dir_stack = grep { !/^\.{1,2}$/ && {$_ = "$cwd/$_"} } @dir_stack; push @stack, reverse @dir_stack; http://stackoverflow.com/questions/8479919/perl-using-loop-or-map-grep opendir $dir_fh, $cwd; foreach my $entry (readdir $dir_fh) { next if $entry =~ /^\.\.?$/; push @stack, "$cwd/$entry"; # or unshift } 2012 Summer Cartwright 6

Computer Sciences 368 Introduction to Perl Ine ffi cient and Unclear my @words; foreach $line (@wordlist) { chomp($line); $line = lc($line); my $found = 0; foreach my $word_ref (@words) { if ($word_ref->[0] eq $line) { $found = 1; $word_ref->[1]++; } } if (not $found) { push(@words, [$line, 0]); } } 2012 Summer Cartwright 7

Computer Sciences 368 Introduction to Perl Good Design is Often E ffi cient and Clear my %words; foreach $line (@wordlist) { chomp($line); $words{lc($line)} += 1; } 2012 Summer Cartwright 8

Computer Sciences 368 Introduction to Perl Script Development 2012 Summer Cartwright 9

Computer Sciences 368 Introduction to Perl Sub-Goal Sub-Goal ??? foreach (sort @tallies) { Sub-Goal Sub-Goal Sub-Goal Sub-Goal Goal next unless $_ > 0; $output .= format($_); } strftime(…) if (exists $hash{$key}) { … } foreach (@list) { … $_ … ; $string =~ s/…/…/ig; } unless (system(…)) { die "… $!\n"; open(my $f, '<', $filename) $count += 1; } or die "...: $!\n"; my @lines = <$f>; sub write_file {} split(/,/, @lines) close($f); 2012 Summer Cartwright 10

Computer Sciences 368 Introduction to Perl (Design, Code, Test)+ Refactor Mercilessly 2012 Summer Cartwright 11

Computer Sciences 368 Introduction to Perl HW #14: Phase I # Read and process forecasts # Read and process observations # Foreach forecast, compare to observations # Print report 2012 Summer Cartwright 12

Computer Sciences 368 Introduction to Perl HW #14: Phase II # Read and process forecasts open(my $forecast_fh, '<', $FORECAST_FILE) or die "open $FORECAST_FILE: $!\n"; while (my $forecast_line = <$forecast_fh>) { chomp($forecast_line); print "$forecast_line\n"; } close $forecast_fh; # Read and process observations # Foreach forecast, compare to observations # Print report 2012 Summer Cartwright 13

Computer Sciences 368 Introduction to Perl HW #14: Phase III sub read_file() { ... } # Read and process forecasts my @f_lines = read_file($FORECAST_FILE) or die "open $FORECAST_FILE: $!\n"; foreach my $forecast_line (@f_lines) { chomp($forecast_line); print "$forecast_line\n"; } # Read and process observations # Foreach forecast, compare to observations # Print report 2012 Summer Cartwright 14

Computer Sciences 368 Introduction to Perl HW #14: Phase IV sub read_file() { ... } # Read and process forecasts my @f_lines = read_file($FORECAST_FILE) or die "open $FORECAST_FILE: $!\n"; my %forecasts; foreach my $forecast_line (@f_lines) { chomp($forecast_line); # print "$forecast_line\n"; my ($date, $time, $high, $low) = split("\t", $forecast_line); $forecasts{$date} = [$high, $low]; } print Dumper(\%forecasts); 2012 Summer Cartwright 15

Computer Sciences 368 Introduction to Perl Questions? 2012 Summer Cartwright 16

Computer Sciences 368 Introduction to Perl Thank You! 2012 Summer Cartwright 17