Red Flags in Programming

Red Flags in Programming Doing things that are probably... not good for us

Some words of caution... We Perlers have a saying... TIMTOWTDI Be nice, no flaming (only I'm allowed) Not a Perl lecture, more like “bad programming habits” “Your mileage may vary”, “no batteries included”, “don't drink and drive”

: #1 ag Repeated code Fl We overlook repeated patterns without even noticing N more to read, understand, debug, test, maintain N more places to have bugs! Updating multiple places is error prone.. it's boring distracting lose focus make mistakes OMFG BUGZ! Really, the worst thing a programmer can do

: #1 ag Repeated code Fl Abstract your code... correctly! Class? Abstract Class? (role) Package? Collection of Functions? Loops? Switches? Dispatch tables?

: #2 ag Reinvent the Wheel Fl You probably won't do it better... seriously Development and maintenance grows because you now have another (usually big) chunk of code It's just repeated code, really...

: #2 ag Reinvent the Wheel Fl Modules Libraries Roles Frameworks Whatever the hell [Free] Pascal has Write patches for what doesn't work for you In extreme cases reinvent, but try to implement as little as required. Sometimes it's necessary to do it all from scratch: Perlbal, Git, Linux :)

: #3 ag Switches without default Fl Not always wrong if ( is_alpha($num) ) {} Usually wrong Unexpected behavior elsif ( is_numeric($num) ) {} Not the worst of things... but please think of it

: #3 ag Switches without default Fl if ( is_alpha($num) ) {} elsif ( is_numeric($num) ) {} else { }

: #4 ag Long Switches Fl Gross, really given ($foo) { Not fun to read or debug Not easily maintainable when (/^10$/) {} It's basically a long if() when (/^20$/) {} elsif()... even if seems when (/^30$/) {} otherwise default {} }

: #4 ag Long Switches Fl Dispatch tables my %dispatch = ( (if you can) Use code references in 10 => CODEREF, switches instead of code 20 => CODEREF, itself 30 => CODEREF, (if you can) ); $dispatch{$num}->();

: #5 ag Try and Catch (workflow) Fl Try and Catch isn't for try { workflow!! That's what we have do_something_simple(); conditions and loops for } catch { Internal functions should print “Dear god, this is a have return codes, not throw exceptions really stupid thing to do!”; PHP is fscking stupid } Try and Catch is for when external functions might crash the program

: #5 ag Try and Catch (workflow) Fl Functions, subroutines, do_something_simple() return codes! Try and Catch is for or die “you suck!n”; external programs or things that are suppose to crash

: #6 ag String Booleans Fl The string “false” is if ( $bool eq 'true' ) { actually true => confusing! Unnecessary value DO SOMETHING check/comparison } elsif ( $bool eq 'false' ) { Misses the point of DO SOMETHING booleans. } $bool = 'false'; if ( $bool ) { BUG }

: #6 ag String Booleans Fl Use real booleans $bool = do_that(@params); Use zero (0), empty strings and undefined variables if ($bool) { Sometimes you can't # wheee... actual booleans control it (using modules, etc.) }

: #7 ag External Binaries Fl Compatibility problems Portability problems Unexpected results (`ps` for example is different on BSD and has different command line switches) Insecure!

: #7 ag External Binaries Fl Shared libraries Bindings APIs libcurl is an example Modules for running binaries more safely and controllably (IPC::Open3, IPC::Open3::Simple, IPC::Cmd, Capture::Tiny) Taint mode (if language supports it – Perl does!) Sometimes you can't control it (external binaries, closed programs, dependencies at $work)

: #8 ag Intermediate Programs Fl Quite possibly insecure Hard to maintain No damned syntax highlighting!!!11

: #8 ag Intermediate Programs Fl If same language, use a subroutine/function Different language && use an Inline module Else, use templates External file

: #9 ag Empty if() Clauses Fl Not DWIM/SWYM if ( $something ) { Having an empty if() for the sake of the else().. is # do nothing horrible } else { CODE }

: #9 ag Empty if() Clauses Fl SWYM... please? if ( !$something ) { Use unless() [Perl] Don't really use unless() CODE } unless ( $something ) { CODE } * Shlomi Fish is allowed to do otherwise :)

0: #1 ag Array Counters Fl Some older languages foreach my $i ( 0 .. $n ) { have no way to know how many elements are in an $array[$i] = 'something'; array... $array_counter++; Some people are too } used to older (more low level) languages Some people don't know there's a better way

0: #1 ag Array Counters Fl Higher level languages have no problem Using the number of the print $#array + 1; last element The number of elements print scalar @array;

1: #1 ag Variable abuse Fl Are you kidding me? sub calc_ages { Awful awful awful The reasons people get my ( $age1, $age2, $age3, their hands chopped off in $age4 ) = @_; indigenous countries } calc_ages( $age1, $age2, $age3, $age4 );

1: #1 ag Variable Abuse Fl That's why we have my @ages = @_; compound data structures (arrays, hashes) my %people = ( Even more complex data dad => { structures, if you want brothers => [], sisters => [], }, }, };

2: #1 ag C Style for() Loop Fl Not really an issue for ( $i = 0; $i < 10; $i++ ) { Harder to understand And just not needed … }

2: #1 ag C Style for() Loop Fl Higher level languages foreach my $var (@vars) { have better/cooler things foreach (where available) ... }

3: #1 ag Goto Hell Fl OMGWTF?!1 if ( something_happened() ) { But seriously folks, goto() strips away all of our ability WHINE: say_it('happened'); to profoundly express my $care = your($feelings); ourselves using languages if ( !$care ) { that finally let us And yes, if you use goto WHINE; goto(), I also think your } mother is promiscuous }

3: #1 ag Goto Hell Fl DON'T USE GOTO! if ( something_happened() ) { You're not a hardcore assembly programmer, my $care; you shouldn't have while ( !$care ) { spaghetti code say_it('happened'); Even xkcd agrees with me! $care = your($feelings); } }

ff tu s od Dry, Rinse, Repeat go e m so DRY (Don't Repeat Yourself) Don't duplicate code, abstract it! KISS (Keep It Simple, Stupid) Don't write overtly complex stuff. Clean design yields clean code. (yet some things are complex, I know...) YAGNI (You Aren't Gonna Need It) Start from what you need. Work your way up.

Thank you.

Red Flags in Programming

by xSawyer on Jul 05, 2009

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