XKCD was interesting today

[DJPhil]

I'm sure some of you have heard of the webcomic XKCD. Today's was a good one for electronics, and I thought you guys might enjoy it.

http://www.xkcd.com/730/#

I think my favorite bit was the arena.

[GeoffS]

I was going to make it but my local supplier is all out of flux capacitors 

[David]

That would make a nice t-shirt!

[JoeB83]

That's a good one. 

[AlfBaz]

hit random a few times and came across this... would been handy in that thread we had about using goto

[free_electron]

I don't understand the fuss about the usage of 'goto'.
even the most 'properly' constructed code will compile down to using JMP instructions. which is nothing more than a goto.

[T3sl4co1l]

Not necessarily true -- although I don't know of any languages which compile semantic constructs into e.g. function calls.  That is, putting the inner braces of each execution path into their own functions.  And by function, I mean, using CALLs instead of JMPs.

But the higher level semantics are much more valuable than the machine code that implements it, at least for average development.  In this post-computational-abundance world, the programmers' bandwidth is the limiting factor.  (Well, almost.  One would hope.  Of course, more computing power always means bigger and slower high level libraries, or scripting languages.  So...)

And, that said, I would enjoy if assembler were designed with indentation in mind.  Many (older?) assemblers won't even accept it -- they expect strict whitespacing.  That makes it very hard to read and write structured code.  Usually, big comment blocks are used.

Tim

[AndyC_772]

goto xkcd

[ECEdesign]

If you hover over the image on the website it says:

"The last band of color indicates the snake's tolerance for being held before biting." 

[rolycat]

Yesterday's strip was good, and (somewhat) electronics related:



The most powerful hand-held torch (flashlight) I could find is the X-LED XHP DualBeam, which the manufacturers reckon is 50,000 lumens.
They are apparently working on a 1 million lumen LED light, but since this will consume 5 kW you probably won't be able to slip it in your pocket.

[AF6LJ]

I'm sure some of you have heard of the webcomic XKCD. Today's was a good one for electronics, and I thought you guys might enjoy it.

http://www.xkcd.com/730/#

I think my favorite bit was the arena.

Been around for a long time but still funny as hell.

[IanB]

The most powerful hand-held torch (flashlight) I could find is the X-LED XHP DualBeam, which the manufacturers reckon is 50,000 lumens.
They are apparently working on a 1 million lumen LED light, but since this will consume 5 kW you probably won't be able to slip it in your pocket.

Well, put two 28 V power tool batteries in series and that will give you 56 V. Such batteries can comfortably supply 100 A, so there's 5 kW. More lantern sized than pocket sized perhaps, and it won't run for very long, but it would be cool on a dark night.

[kfitch42]

Well, put two 28 V power tool batteries in series and that will give you 56 V. Such batteries can comfortably supply 100 A, so there's 5 kW. More lantern sized than pocket sized perhaps, and it won't run for very long, but it would be cool on a dark night.

A quick google told me that the Makita 28V battery is 3.0Ah. So, we are talking less than 2 minutes at 100 Amp. I am guessing these things aren't designed for continuous operation at 100A. So, hopefully they won't last long enough to heat up to thermal runaway...

But, at least you will be able to see what you are doing while jump starting a big diesel truck:

[tszaboo]

I don't understand the fuss about the usage of 'goto'.
even the most 'properly' constructed code will compile down to using JMP instructions. which is nothing more than a goto.

Because memory leak, and dinosaurs.

BTW if you want bright flashlights, try them with Maxwell supercapacitor banks. 75V 1800A from something that fit into a backpack.

[HackedFridgeMagnet]

Had this one on the fridge. My son was fascinated by it even though he was young and didn't know what SQL was.




https://xkcd.com/1133/
Is currently on the fridge:

[suicidaleggroll]

In addition to the above, I like these ones:


and

[Delta]

goto xkcd

Well played, Sir.
Well played!

[rs20]

I don't understand the fuss about the usage of 'goto'.
even the most 'properly' constructed code will compile down to using JMP instructions. which is nothing more than a goto.

Because memory leak, and dinosaurs.

Ironically, I have a soft spot for goto in one particular usecase: preventing memory leaks on error conditions (athough I don't use it in this situation professionally, and I generally abhor goto in every other case). Example:

Code: [Select]

void main() {
  FILE* f1 = fopen( ... );
  if (f1 == NULL) {
    printf("Failed to open f1\r\n");
    return;
  }

  Object a = makeObject();
  if (a == NULL) {
    printf("Failed to make a\r\n");
    goto finalize_f1;   
  }

  ...

  if (nasty.error()) {
    printf("Ouch\r\n");
    goto finalize_a;
  }

  ...

finalize_a:
  a.finish();
  delete a;
finalize_f1:
  fclose(f1);
}

Obviously in this case the Object could have been allocated on the stack; but it's more the problem of issuing cleanup method calls like close() -- which may well delete objects internally. Of course more featured languages have things like the defer block, which is one of many ways to avoid this pattern.

[IanB]

Ironically, I have a soft spot for goto in one particular usecase: preventing memory leaks on error conditions (athough I don't use it in this situation professionally, and I generally abhor goto in every other case). Example: ...

In C++ the RAII pattern can be used to good effect where resource cleanup should happen for all exit paths including errors and exceptions.

[rs20]

Ironically, I have a soft spot for goto in one particular usecase: preventing memory leaks on error conditions (athough I don't use it in this situation professionally, and I generally abhor goto in every other case). Example: ...

In C++ the RAII pattern can be used to good effect where resource cleanup should happen for all exit paths including errors and exceptions.

Indeed, I really like RAII, although it's not available in pure C of course. I've been meaning for a while to see what the overhead for using C++ on AVR is...

[Delta]

I'm just learning C, so don't have a clue, but...

I fully understand that abusing goto can result in awful spaghetti code, but the "thou shalt not us goto under any circumstances" mantra seems almost cult-like!

[JoeO]

I'm just learning C, so don't have a clue, but...

I fully understand that abusing goto can result in awful spaghetti code, but the "thou shalt not us goto under any circumstances" mantra seems almost cult-like!

C code can be written without using GOTOs. 

[Maxlor]

I'm just learning C, so don't have a clue, but...

I fully understand that abusing goto can result in awful spaghetti code, but the "thou shalt not us goto under any circumstances" mantra seems almost cult-like!

You can break the rules once you've mastered them, but not before. It's neither a mantra nor cult-like, it's just something meant to preserve as much global sanity as possible.

[Delta]

I'm just learning C, so don't have a clue, but...

I fully understand that abusing goto can result in awful spaghetti code, but the "thou shalt not us goto under any circumstances" mantra seems almost cult-like!

C code can be written without using GOTOs.

I'm sure it can be written without using a lot of things!  So surely that's not a reason by default. 

I have read a fair bit about this on stackexchange and other sites, and it seems that people will go to (pun not intended, sorry) extreme lengths, writing convoluted code, just to avoid a goto!  That's when it seems to me like more dogma than engineering!

[Delta]

I'm just learning C, so don't have a clue, but...

I fully understand that abusing goto can result in awful spaghetti code, but the "thou shalt not us goto under any circumstances" mantra seems almost cult-like!

You can break the rules once you've mastered them, but not before. It's neither a mantra nor cult-like, it's just something meant to preserve as much global sanity as possible.

I am looking forward to that day!