fuckyeahterminals

“Why are unions in c useful?” I was actually driven to write this post because I couldn’t find any compelling examples of the utility of the union keyword in C. There were a lot of great examples of reference material breaking down the differences between struct and union and the mechanics of union, but not a lot depicting what I felt was a compelling example of how union could be powerful. I only found one that I felt was exemplary but it dealt with it at the byte level, which is great if you’re doing embedded programming, but not relatable all if you’re coming from a different background. So I’ll give a short direct explanation for how I was able to wrap my brain around union and why I think this mental model is better than a lot of the explanations on the internet. I think of union as a way of declaring members in a group that overlap one another in the same area of memory. That immediately clarifies the behavior of union and why things need to be accessed “one at a time”. Really what it means is you’re referencing the same block of memory. disclaimer: I don’t know if that’s actually how it works but I went ahead and wrote a program to see if I could validate my mental model, and lo and behold it worked. So here’s an example I would call useful. Consider this: you’re writing code for a business that sells books at scale, you need it to be performant, or maybe it’s a really old system - at any rate you have to write it in C. You sell physical books and are extending the system to sell eBooks, so naturally you think to yourself “it’d be great if I could just write the extension and leave most of the existing code alone.” Let’s see some sample code, contemplate the following snippet as part of your existing code

struct Paperback { char bookId[25]; char bookTitle[200]; char author[200]; }; void printPaperbackInfo(struct Paperback pb) { printf( "This is a book with ID %s and Title of %s written by %s.\n", pb.bookId, pb.bookTitle, pb.author ); } int main(int argc, char* argv[]) { struct Paperback theFall; strcpy(theFall.bookId, "PHY255ACTF"); strcpy(theFall.bookTitle, "The Fall"); strcpy(theFall.author, "Albert Camus"); printf("Okay so far we have...\n"); printPaperbackInfo(theFall); }

You think to yourself, “Okay, well I need to add some concepts about eBook so I’d probably create an eBook specific stuff and use it as I need it.” So that’s what you do:

struct ElectronicBook { char bookId[25]; char bookTitle[200]; char author[200]; char format[10]; char DRMS[50]; }; void printElectronicBookInfo(struct ElectronicBook eb) { printf( "This is a book with ID %s and Title of %s written by %s.\n", eb.bookId, eb.bookTitle, eb.author ); printf( "This book is in format %s signed with %s.\n", eb.format, eb.DRMS ); }

Well now you notice you have duplicated code. There also seems to be a lot ElectronicBook and Paperback share in common. Either way you’re left wondering something to the effect of “I guess I could re-use void printPaperbackInfo(struct Paperback pb) and just cast my structs everytime I want to use it, but either way I have two distinct structs I’d be using and really I wish I had the one.” Enter union. So at this point I would say, “Hey I want a union of these two data structures, because they’re basically the same thing in memory with some added stuff, and I don’t want to be casting stuff all the time and having to deal with compiler errors” so your code would evolve to look like this

struct Paperback { char bookId[25]; char bookTitle[200]; char author[200]; }; struct ElectronicBook { char bookId[25]; char bookTitle[200]; char author[200]; char format[10]; char DRMS[50]; }; union Book { struct Paperback pb; struct ElectronicBook eb; }; void printPaperbackInfo(struct Paperback pb) { printf( "This is a book with ID %s and Title of %s written by %s.\n", pb.bookId, pb.bookTitle, pb.author ); } void printElectronicBookInfo(struct ElectronicBook eb) { printf( "This book is in format %s signed with %s.\n", eb.format, eb.DRMS ); }

okay well now we have some definitions, this seems strictly better than the previous duplicated code we had, let’s see where this goes Its usage might look something like:

int main(int argc, char* argv[]) { union Book theFall; strcpy(theFall.pb.bookId, "PHY255ACTF"); strcpy(theFall.pb.bookTitle, "The Fall"); strcpy(theFall.pb.author, "Albert Camus"); printf("Okay so far we have...\n"); printPaperbackInfo(theFall.pb); // but wait maybe we reach out to some part of our system // and discover this is available as an eBook and we // want to treat it as such now printf("We're assigning ebook data\n"); strcpy(theFall.eb.format, "kindle"); strcpy(theFall.eb.DRMS, "Digital Rights Management Signature"); printf("That's cool the paperback code is still happy...\n"); printPaperbackInfo(theFall.pb); printf("But so is the eBook code...\n"); printElectronicBookInfo(theFall.eb); return 0; }

This is to all those sites who will “physically” not load content onto a page because there’s an ad-blocker running on my machine, essentially “blocking” my ad-blocker. 

I don’t care enough about your content to make a change in my habits.

And my suspicion is, those that care enough to install an ad-blocker probably feel the same way. You’re effectively lowering your user-base and increasing into your opportunity cost. I will literally without hesitation or remorse navigate away and let the article and it’s contents die and escape any previous interest I’ve might’ve originally had.

The real cost to you. Diffusion of material to those that don’t have that turned on. You’re truncating the graph or tree outgrowth of the diffusion of information to those nodes that really dislike advertisement, because really, what do I care about whatever your shitty ad-server is going to try and sell me?

Downright coldblooded.

I would do something more subtle like:

alias ls="ls -alh | head"

the best thing I’ve seen all day

class support now comes on by default on Chrome following this 49 release. So basically if you’re dev-ing for chrome you can use classes in your javascript now. 

fuckyess, Hopefully this mean that front-end .js code will be less of a clusterfuck now.

It's basically the difference between this bullshit:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects#Using_a_constructor_function 

to:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes 

I totally forgot I had this laying around. Someone asked me for it the other day. here you go.

https://github.com/lvalencia/EulerProject

I could hear an evil laugh going off in my head as I wrote this.

($el.is('i')) ? $el = $el.parents('h4') : '' ;

you know technically I can assign this statement to a variable that wont presist.

[].useless = ($el.is('i')) ? $el = $el.parents('h4') : '' ;

Just 'cuz.

By virtue of the language I end up writting stuff like this.

public function getLatestScoreForExam($exam) { $scores = array(); for ($i = 1, $score = "N/A"; !empty($score); $i++) { array_push($scores, $score); $score = $exam->getData('attempt_'.$i); } return array_pop($scores); }

What's worse some people will think this is "good" or "clever".

cat expenses | awk -F'$' '{print $NF}' | paste -sd+ - | bc

I don’t usually ask questions, but I’m watching the Keynote for Polymer because I was really intrigued with Google Material Design (so I was reading their manifesto and ended up clicking out) -- and, how is Polymer and Web Components any different (conceptually) than XAML?

I mean XAML is deeply integrated with the Microsoft Workflow, so contextually I understand that that is a major distinction, i.e. at this point in time you cant use XAML unless you’re developing using the Microsoft Ecosystem.

But if we strip that out, then it’s essentially the same concept, except it plays nicely with everything. I mean don’t get me wrong, I like what I’m hearing them say.

But they’ve stayed that “[it] isn’t simply a better version of something else out there, it’s not like things that came before” and that they’re “... [doing] something totally new, and build on something revolutionary and dramatically change web development. So get right out right on the bleeding edge of standards, and start pushing and vetting new concepts”