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Thread Rules
1. This is not a "do my homework for me" thread. If you have specific questions, ask, but don't post an assignment or homework problem and expect an exact solution.
2. No recruiting for your cockamamie projects (you won't replace facebook with 3 dudes you found on the internet and $20)
3. If you can't articulate why a language is bad, don't start slinging shit about it. Just remember that nothing is worse than making CSS IE6 compatible.
4. Use [code] tags to format code blocks. |
On January 28 2017 00:03 travis wrote:
Is it ok if I come to this thread with questions related to my "discrete structures" course? It isn't programming, but it is computer science.
Yea sure. If you have decent math background that course is gonna be aggravatingly boring. If you've not had a proof based math course (analysis, algebra, etc), then it should be pretty important.
On January 28 2017 00:23 mantequilla wrote:
Why do you need them (vim emacs) when nearly everything has a good IDE that's tailored specifically to whatever you do?
never used/installed them just asking.
I used to use IDE pretty much exclusively until I started working on codebases that were so large that the IDE all grind to a halt on a routine basis. It would be awesome if visual studio or something scaled well enough (and in practice, you can kinda hack in plugins to eclipse to make some operation bareable, especially if you're only working on the same specific tiny subsection of code, and not syncing often).
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On January 28 2017 03:04 Acrofales wrote:Show nested quote +On January 28 2017 02:52 Silvanel wrote:
Well the obvious answer is that a text editor can be used for many things besides developing. Many devices run Linux/QNX with basic text editors so if You are in need of editing some config file quickly its very handy.
I will give You an example:
I am working with embedded device that is running QNX. I need to change some paramteres inside config file on device. Now i can change conifguration of my ethernet card, remount the devices file system then copy the config file to shared folder edit it on my comp and copy edited file back. Takes about 2 minutes.
Or i can open this file in vi (which is part of QNX devices build) and edit it on device itself. Takes about 20 seconds.
I mean You dont need tu use Vi/Vim or whatever as Your IDE but knowing it just helps (sometimes). Or you can open it in nano/pico/whatever, and not have to know that you first have to hit "a" (or "i") to be able to type at all, then esc to get back to normal mode, and then :wq to save and quit. And one of those is equally or more likely to be installed on a bare linux system than vi (let alone vim or emacs). vim/emacs is useful for editing code, because you actually have to switch files and do complicated edit operations. not because you have to edit some random file in your /etc directory. I don't know anything about QNX, so I assume you actually need vi for that. But that seems overly specific for a university course 
This is overly specific even for real life jobs. I mean i didnt check the data but i have a feeling that embedded jobs are minority on the market. I just felt like sharing a story
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On January 26 2017 20:58 Silvanel wrote:So i have a C question. What exactly is difference between: a = a + 1 and a = a++ + Show Spoiler +?? more specifically why:
#include <stdio.h>
int main () {
int a = 10;
do {
printf("Value of a: %d\n", a);
a = a + 1 ;
} while ( a <20 );
return 0;
}
and
#include <stdio.h>
int main () {
int a = 10;
do {
printf("Value of a: %d\n", a);
a = a++ ;
} while ( a <20 );
return 0;
}
give different results? (The latter creates an endless loop) Edit:Nevermind got an answer myself, spoilered so evidence of my stupidity is not forgoten.
Could someone help me figure out why the second version results in an endless loop:
to me it seems like the operations carried out should be a = a(thus retaining the original value, not advancing the loop)
but THEN the "++" should be happening and the value stored in a(which at this point should be a = a, i.e. the unchanged a) should be incremented before being used in the predicate.
Why does the "++" get lost?
edit to clarify:
my understanding is that the value in a is the original not yet incremented value at the end of the line "a = a++;" but after that, in the while() it should already have been incremented
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Cause in C,
x = a++ will increase value of a by one but return value before increment whereas
y = ++a will increase value of a by oneand return value after increment
Edit:
Cause if You do soemthing like a = a++ the increment is lost as i understand it. The assiagned value is value before increment so nothing relevant really happens.
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On January 28 2017 19:58 deus.machinarum wrote:Show nested quote +On January 26 2017 20:58 Silvanel wrote:So i have a C question. What exactly is difference between: a = a + 1 and a = a++ + Show Spoiler +?? more specifically why:
#include <stdio.h>
int main () {
int a = 10;
do {
printf("Value of a: %d\n", a);
a = a + 1 ;
} while ( a <20 );
return 0;
}
and
#include <stdio.h>
int main () {
int a = 10;
do {
printf("Value of a: %d\n", a);
a = a++ ;
} while ( a <20 );
return 0;
}
give different results? (The latter creates an endless loop) Edit:Nevermind got an answer myself, spoilered so evidence of my stupidity is not forgoten. Could someone help me figure out why the second version results in an endless loop: to me it seems like the operations carried out should be a = a(thus retaining the original value, not advancing the loop) but THEN the "++" should be happening and the value stored in a(which at this point should be a = a, i.e. the unchanged a) should be incremented before being used in the predicate. Why does the "++" get lost? edit to clarify: my understanding is that the value in a is the original not yet incremented value at the end of the line "a = a++;" but after that, in the while() it should already have been incremented
int a = 5;
a = a++;
assert(a == 5);
The postfix increment first returns the old value, that is 5, then it increments it. The assignment has not yet been done at this point in time! a has the value 6 but the increment operator returned the value 5. Now a gets assigned to the returned value (here: 5).
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On January 28 2017 19:58 deus.machinarum wrote:Show nested quote +On January 26 2017 20:58 Silvanel wrote:So i have a C question. What exactly is difference between: a = a + 1 and a = a++ + Show Spoiler +?? more specifically why:
#include <stdio.h>
int main () {
int a = 10;
do {
printf("Value of a: %d\n", a);
a = a + 1 ;
} while ( a <20 );
return 0;
}
and
#include <stdio.h>
int main () {
int a = 10;
do {
printf("Value of a: %d\n", a);
a = a++ ;
} while ( a <20 );
return 0;
}
give different results? (The latter creates an endless loop) Edit:Nevermind got an answer myself, spoilered so evidence of my stupidity is not forgoten. Could someone help me figure out why the second version results in an endless loop: to me it seems like the operations carried out should be a = a(thus retaining the original value, not advancing the loop) but THEN the "++" should be happening and the value stored in a(which at this point should be a = a, i.e. the unchanged a) should be incremented before being used in the predicate. Why does the "++" get lost? edit to clarify: my understanding is that the value in a is the original not yet incremented value at the end of the line "a = a++;" but after that, in the while() it should already have been incremented
a++ returns a copy of a before the increment. The ++ increases the original value, but not the copy that afterwards gets assigned back to a.
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ok I get that because the value of the return is put into a different variable/memory location but after x = a++ happened the value in a should also have been incremented, right?
so, going back to the original code, "whenever" the ++ happens it should increment the value stored in a after the whole statement is done or maybe the result of the ++ is thrown out because it is not returned?
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On January 28 2017 20:13 deus.machinarum wrote:
ok I get that because the value of the return is put into a different variable/memory location but after x = a++ happened the value in a should also have been incremented, right?
so, going back to the original code, "whenever" the ++ happens it should increment the value stored in a after the whole statement is done or maybe the result of the ++ is thrown out because it is not returned?
a = a++ is exactly the same as
int temp = a;
a = a + 1;
a = temp;
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On January 28 2017 20:18 Morfildur wrote:Show nested quote +On January 28 2017 20:13 deus.machinarum wrote:
ok I get that because the value of the return is put into a different variable/memory location but after x = a++ happened the value in a should also have been incremented, right?
so, going back to the original code, "whenever" the ++ happens it should increment the value stored in a after the whole statement is done or maybe the result of the ++ is thrown out because it is not returned? a = a++ is exactly the same as int temp = a;
a = a + 1;
a = temp;
ok thx, that cleared it up for me 
also thx to everyone taking time to respond
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On January 28 2017 20:18 Morfildur wrote:Show nested quote +On January 28 2017 20:13 deus.machinarum wrote:
ok I get that because the value of the return is put into a different variable/memory location but after x = a++ happened the value in a should also have been incremented, right?
so, going back to the original code, "whenever" the ++ happens it should increment the value stored in a after the whole statement is done or maybe the result of the ++ is thrown out because it is not returned? a = a++ is exactly the same as int temp = a;
a = a + 1;
a = temp;
Sorry, but that's actually incorrect. The semantics of this statement is *undefined*, because = does not introduce a sequence point.
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But why would you ever type a = a++; (except as a typo from ignorance)? The whole point of a++ is that it's shorthand for incrementing by 1. So if you use ++, you write it:
#include <stdio.h>
int main () {
int a = 10;
do {
printf("Value of a: %d\n", a);
a++ ;
} while ( a <20 );
return 0;
}
And voila, it works fine. The moment you start writing things with a = <do something with a>, you have to worry about operator precedence (in fact, any time you use multiple operators you have to think about that).
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It's funny how so many of these programming discussions are about the ++ operator... Which is one of the least interesting parts of programming. Instead of concentrating on cool/weird syntax people should focus more on solving actual problems.
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Did y'all know that Java enums can implement interfaces? Simply declare the interface and add the extra methods to the enum and each member of the enum implements it.
public enum Mode implements Iterable{
ON, OFF, STANDBY;
public Iterator iterator() {
return null;
}
}
Are there any common design patterns where this is useful?
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On January 29 2017 06:00 fmod wrote:
It's funny how so many of these programming discussions are about the ++ operator... Which is one of the least interesting parts of programming. Instead of concentrating on cool/weird syntax people should focus more on solving actual problems.
Trying to solve problems without understanding the syntax you're using only creates more problems.
It's like asking why someone would bother learning English when they should just start writing novels.
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The ++ operators should never have been created in the first place. The potential for legitimate use is greatly outweighed by people trying to be "clever" and failing hard.
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On January 29 2017 05:24 Acrofales wrote:But why would you ever type a = a++; (except as a typo from ignorance)? The whole point of a++ is that it's shorthand for incrementing by 1. So if you use ++, you write it:
#include <stdio.h>
int main() {
int a = 10;
do {
printf("Value of a: %d\n", a);
a++ ;
} while ( a <20 );
return 0;
}
And voila, it works fine. The moment you start writing things with a = <do something with a>, you have to worry about operator precedence (in fact, any time you use multiple operators you have to think about that).
#include <stdio.h>
int main(void)
{
int a = 10;
do {
printf("Value of a: %d\n", a);
} while (a++ < 20);
return 0;
}
That's how you do it (if you really want to use the ++ operator)
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Well, i am learning C. I started playing with code (changing and looking what happenes) was surprised with endless loop at first. Dont You guys play with code when You are learning something?
I am suprised it got so much attention
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On January 29 2017 06:27 Buckyman wrote:Did y'all know that Java enums can implement interfaces? Simply declare the interface and add the extra methods to the enum and each member of the enum implements it. Show nested quote +
public enum Mode implements Iterable{
ON, OFF, STANDBY;
public Iterator iterator() {
return null;
}
}
Are there any common design patterns where this is useful?
Enums are just regular old classes with some additional rules applied to them (only private constructors for example) but the added benefit of a few neat compiler-magic features. Each enum constant is actually its own annonymous class and can re-implement most methods as it chooses. The equals, hashCode and ordinal methods (and probably some others too) for enums are final though.
Where is this useful? Well, I can imagine default-methods in Java8 being pretty useful for enums. On top of that it might help you structure your program better with clearly defined API's. Enums could be used as static final instances of an interface but you may construct more instances dynamically with another class.
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On January 29 2017 06:39 spinesheath wrote:
The ++ operators should never have been created in the first place. The potential for legitimate use is greatly outweighed by people trying to be "clever" and failing hard.
It's useful when you want to replace for loops with while loops (which is done behind the scenes by the compiler anyway, since for is just an alias for while). It saves you but a line of code compared to the proper while loop, but if your project will have thousands of those, it's thousands of lines saved.
ex:
for (int i = 0; i < 10; i++) {
// do stuff
}
// ^ translates to
int i = 0;
while (i < 10) {
// do stuff
i += 1;
}
Now, I prefer to write it this way:
int i = 0;
while (i++ < 10) {
// do stuff
}
I prefer to use while over for whenever I can, mostly because I like to declare and initialize all the variables at the beginning of a function. Makes it easier to debug later on, even if it isn't the most efficient thing to do.
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EPT
