The Big Programming Thread - Page 240

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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.

Arnstein

Norway3381 Posts

February 07 2013 08:06 GMT

#4781

How can I get a random number between 65 and 65+LETTERS? Right now I use this:
rand() % (LETTERS+65) +65

as I found on a C++ reference web page, but that certainly gives me more stuff than only numbers in range 65-65+LETTERS!

KaiserJohan

Sweden1808 Posts

February 07 2013 08:12 GMT

#4782

Get used to working in an IDE because that is what you will do most of the time anyway.
Plus when you know one IDE, it's not THAT hard to get into others, and you know what to look for.

Tobberoth

Sweden6375 Posts

February 07 2013 08:18 GMT

#4783

On February 07 2013 06:58 ChrisXIV wrote:

Show nested quote +

Ah yes, IDE, don't know why I keep forgetting that word.

Hm, that sucks. It's just that clicking through all those options in VS with no idea what they do...oh well, text editor it is, thank you.

I really recommend learning and using Visual Studio. Not only will it definitely be what you work with professionally in the future if you work with windows development, its intellisense is out of this world, once you get used to it, using any other IDE is a dread. Safe to say, Visual Studio is quite a big program to learn and might be daunting at first, but it's surprisingly easy to use once you're used to it and can be customized beyond belief as in what windows it shows etc. It's also ridiculously powerful once you get to know some of the features such as debugging etc.

I'm pretty sure there are tutorials on how VS works and you would only need to know the most important options to start (starting a project, adding classes, building). Personally I only knew how to program Java and Python but was hired as a C# programmer. Learned C# is about a week and started using VS at work immediately. At first it was confusing, but I got used to it very quickly... with a decent manual or tutorial, you should be up and running in no-time.

Abductedonut

United States324 Posts

February 07 2013 08:32 GMT

#4784

On February 07 2013 17:06 Arnstein wrote:
How can I get a random number between 65 and 65+LETTERS? Right now I use this:
rand() % (LETTERS+65) +65

as I found on a C++ reference web page, but that certainly gives me more stuff than only numbers in range 65-65+LETTERS!


#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>

int main(int argc, char *argv[])
{
  srand( time(NULL) );
  int LETTERS = 96;
  
  for ( int i = 0; i < 100; i++ )
  {
      printf("Random number: %i \n", rand()%(LETTERS-65)+65  );
  }
  
  system("PAUSE");	
  return 0;
}

It's rand()%(LETTERS-65)+65

*edit* This is obviously assuming LETTERS > 65. Otherwise, you need absolute value.

*edit* If you want to impress your teacher:
rand()%( (LETTERS > 65) ? LETTERS-65 : 65-LETTERS) + 65

Be careful though, if LETTERS == 65 you're boned..

Arnstein

Norway3381 Posts

February 07 2013 08:42 GMT

#4785

Letters is actually a CONST INT sat to 6. I am trying to make a function that makes a random char from a-f. So then I would have to get a random number from 65-71. (I am told to use the const though)

Abductedonut

United States324 Posts

February 07 2013 09:08 GMT

#4786

On February 07 2013 17:42 Arnstein wrote:
Letters is actually a CONST INT sat to 6. I am trying to make a function that makes a random char from a-f. So then I would have to get a random number from 65-71. (I am told to use the const though)


#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>

int main(int argc, char *argv[])
{
  srand( time(NULL) );
  const int LETTERS = 6;
  
  for ( int i = 0; i < 100; i++ )
  {
      printf("Random char: %c \n", rand()%(LETTERS) + 65  );
  }
  
  system("PAUSE");	
  return 0;
}

Arnstein

Norway3381 Posts

February 07 2013 09:15 GMT

#4787

Oh god, I'm so stupid

Thanks a lot!

MisterD

Germany1338 Posts

February 07 2013 20:50 GMT

#4788

On February 07 2013 11:16 darkness wrote:
I'm having a bit of trouble to understand C memory management. Could you please show me an easy to understand guide? What I also need is perhaps some practical examples where it's crucial to deal with memory instead of stack.

Thanks

there isn't actually much to it. system memory is separated into stack and heap like in most languages. your entire heap is essentially one giant array. Firstly, your compiled program lies somewhere in there. Secondly, you can reserve multiple ranges of slots in there (calling malloc(size) returns the memory address called pointer, which you can think of as the "index in the giant array" so to speak, where your reserved section starts) to store your stuff and once you don't need one anymore you give it back to the system (by calling free(pointer); ) so someone else can use it. Dereferencing a pointer essentially just means to access the value stored at the given index. In case of reading from an actual array that you allocated on the heap for example, you can go "the pointer (where the array starts) plus 3 lots further, read the value at this position".

And then you don't pay attention, iterate one index too far, access a location that doesn't actually belong to you, and either the operating system detects it and shuts you down to prevent hacking or your program crashes because someone else put some numbers there that are not what your code is written to handle.

It is the most precise you can get which benefits performance, on the other hand though it's incredibly tedious and annoying and extremely vulnerable for creating bugs. Stack works like any other programming language.

as for what to put on heap and what on stack: If you reserve a block of memory that's only going to be used in the function you are currently in (and maybe some functions it calls, but it will not escape this scope), then it's fine to put it on the stack (as long as it's not HUGE). Advantage is you don't need to clean it up yourself, it disappears as soon as your method is done executing, and it doesn't interact with all the stuff on the heap. Disadvantage is, it will disappear as soon as your method is done executing. so, if you reserve an area to fill it with data, that will survive for longer than your method (say, load an image for later use), then you will need to put it on the heap by manually reserving space there and you will have to manually free the space again once you don't need it anymore.

Note though that it is possible for the compiler to store some data in the heap although you wrote it in a way that looks like it would be on the stack. But that's transparent and you don't need to care about it at all, it won't interfere with your program. Trust your compiler magic!

Mistakes

United States1102 Posts

February 07 2013 21:34 GMT

#4789

Hi all, I'm having some trouble with this SQL statement. It's probably something stupid easy that I'm just looking past but I'd love some advice.

+ Show Spoiler +

alter table l_employees
add constraint l_employees_hire
check (hire_date > #01/01/1995#);

I need to add a constraint that checks for employees that were hired after 1995, and this statement is giving me an error in MS Access for SQL.

Shield

Bulgaria4824 Posts

February 07 2013 21:38 GMT

#4790

Thanks MisterD.

lilwisper

United States2515 Posts

February 07 2013 21:59 GMT

#4791

On February 08 2013 06:34 Mistakes wrote:
Hi all, I'm having some trouble with this SQL statement. It's probably something stupid easy that I'm just looking past but I'd love some advice.

+ Show Spoiler +

alter table l_employees
add constraint l_employees_hire
check (hire_date > #01/01/1995#);

I need to add a constraint that checks for employees that were hired after 1995, and this statement is giving me an error in MS Access for SQL.

Taking a stab at it without being able to see the error code you got, I would say to double check your datatype in hire_date. I believe in Access that the Date datatype handles a bit differently than Text datatype when it comes to doing date comparisons.

Mistakes

United States1102 Posts

February 07 2013 22:04 GMT

#4792

It was a syntax incorrect error on CHECK. I just was reading more about it and it looks like there is no way to write it in SQL/Access, you have to use the GUI to check it. Lol. So I wasn't crazy!

nunez

Norway4003 Posts

February 08 2013 01:10 GMT

#4793

imagine how awful the mangled corpses being put together from your 'compiler' would actually look like, if your computer visualized them to you as creations similar to dr. frankensteins monster.

just... one with legs... JUST legs and one eye. just guts lying around with some hair on it. single nails lying around...

at least mine would be. i need to learn to debug, and not just try to comment out single lines and recompile until i "found the error". i need to learn to debug.

Mistakes

United States1102 Posts

February 08 2013 04:28 GMT

#4794

Hi all, I'm back again with another SQL question through MS Access.

I'm trying to get an output of first names in whole and last names with just one letter, a period, and a space like so:

"Skylar Hoy" in the database in a field called (full_name) to:
"Skylar H. "

This is the code that I have:
+ Show Spoiler +

SELECT employee_id,
first_name & ' ' & last_name as full_name
FROM l_employees;

Seems like anything else I try besides just returning the full name, last name in whole, gives me either an error or the wrong output. Suggestions?

Craton

United States17281 Posts

February 08 2013 05:37 GMT

#4795

Something like

SELECT employee_id, first_name & ' ' & LEFT(last_name, 1) & '.' FROM l_employees;

Probably.

Mistakes

United States1102 Posts

February 08 2013 06:23 GMT

#4796

Awesome, I'll give it a shot when I get home. tyty.

Mistakes

United States1102 Posts

February 08 2013 08:28 GMT

#4797

On February 08 2013 14:37 Craton wrote:
Something like

SELECT employee_id, first_name & ' ' & LEFT(last_name, 1) & '.' FROM l_employees;

Probably.

That worked perfectly! Thank you very much. :D

enigmaticcam

United States280 Posts

February 08 2013 20:00 GMT

#4798

Does anyone here have any experience with iOS development, specifically Core Data? I'm having some issues with multiple persistent stores, where a managed object context using one persistent store will change another managed object context that's using a different persistent store. I can go into more details if needed, but I'm not sure if anyone here has done this kind of thing before.

Shield

Bulgaria4824 Posts

February 09 2013 15:11 GMT

#4799

I'm currently learning C which I wanted to do eventually, but I gotta say Java is a much higher level language. I've realised this when I had to deal with getchar() and putchar(). Also Java's error detection is superior.

I hope C++ surprises me more tho.

Edit: Oh yeah, no built-in threads & classes feature. I've heard of pthread, but isn't this something that doesn't come as standard?

CptCutter

United Kingdom370 Posts

February 09 2013 16:45 GMT

#4800

On February 10 2013 00:11 darkness wrote:
I'm currently learning C which I wanted to do eventually, but I gotta say Java is a much higher level language. I've realised this when I had to deal with getchar() and putchar(). Also Java's error detection is superior.

I hope C++ surprises me more tho.

Edit: Oh yeah, no built-in threads & classes feature. I've heard of pthread, but isn't this something that doesn't come as standard?

I have not learnt any C, but im guessing its similar to programming c++ procedurally. anyways, you will find out that java is amazing for the error messages it gives, but is generally a pain in the ass due to other reasons. And then you will find out that C++ is generally better due to having strict control over pointers, but a pain in the ass when your linking goes screwy or you programmed a large piece of code, and spend hours trying to find the "trying to access wrong memory" error.

I generally tend to prefer C++ even with its annoying error messages because it gives far more control over the programming. C# is nice too.

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