The Big Programming Thread - Page 193
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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. | ||
tofucake
Hyrule18938 Posts
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RoyGBiv_13
United States1275 Posts
On November 15 2012 08:20 tofucake wrote: VHDL is literally Hitler +1. The only thing worse than VHDL is the software used to write ti. | ||
dannystarcraft
United States179 Posts
Needless to say, I was wondering why my console program was magically crashing! Turns out I had run out of physical memory. After deallocating, I am running under 4 MB of memory easy. I would say a vast improvement! ^^ | ||
Craton
United States17216 Posts
On November 15 2012 02:43 white_horse wrote: How hard is it to learn SQL, PHP, C# after you learn C++? I'm an intermediate c++ programmer. It looks like it would be easier since you know a little bit about programming already. Each successive language is easier to learn than its predecessor because you know more fundamentals / core concepts and have a better understanding of how things work. There is no way for someone else to quantify how hard it will be for you to learn a new language. Just run through various tutorials and then start doing personal projects using the different technologies. | ||
Nausea
Sweden807 Posts
I´m passing a pointer to a function and for some reason when inside the function, it got the wrong address. How is this even possible? http://i.imgur.com/SaWNt.jpg http://i.imgur.com/p5JGl.jpg The program works, but getting real undefined behavior. Hope someone can help, thanks. | ||
CecilSunkure
United States2829 Posts
On November 15 2012 10:51 Nausea wrote: Hey, I got a big problem. If anyone know why this is happening, please let me know. I´m passing a pointer to a function and for some reason when inside the function, it got the wrong address. How is this even possible? http://i.imgur.com/SaWNt.jpg http://i.imgur.com/p5JGl.jpg The program works, but getting real undefined behavior. Hope someone can help, thanks. You are probably running debugger in release mode with optimizations on. | ||
Nausea
Sweden807 Posts
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cowsrule
United States80 Posts
On November 15 2012 11:07 CecilSunkure wrote: You are probably running debugger in release mode with optimizations on. There's unfortunately a lot of potential problems here. Is the pointer pointing to the correct location before going into the function call? Inside the function, does the pointer point to garbage, something on the heap, a constant, something on the stack? Can you post a bit more code beyond the function signatures? [Edit: Specifically around the object init and calling of the functions] If the problem ends up being stack corruption, it would be quite difficult to track down without looking through the debugger itself. | ||
Abductedonut
United States324 Posts
On November 15 2012 10:51 Nausea wrote: Hey, I got a big problem. If anyone know why this is happening, please let me know. I´m passing a pointer to a function and for some reason when inside the function, it got the wrong address. How is this even possible? http://i.imgur.com/SaWNt.jpg http://i.imgur.com/p5JGl.jpg The program works, but getting real undefined behavior. Hope someone can help, thanks. HAHAHAHA, I knew someone would eventually run into this problem. C++ is the most trash language in the history of trash languages, and now I shall show you why. Observe: Code #1: + Show Spoiler +
Results: + Show Spoiler + Pointer to kitty: 75F59E34 Address of kitty: 0028FF44 Entered function! Address of kitty: 0028FF20 Pointer to kitty: 75F59E34 Modified Code #2: + Show Spoiler +
Results: + Show Spoiler + Address of kitty: 0028FF44 Entered function! Address of kitty: 0028FF44 Thehehehe. Can you figure out what went wrong! Ruh roh! *EDIT* Okay... I feel bad for those less-experienced programmers who are going to look at my post and go "I don't get at all what's happening"... Here's the deal: Primitive types that C++ derives from C such as int,char,float etc etc... and ARRAYS/POINTERS to these primitive types always pass the ADDRESS of the variable, which means regardless of whether your function signature uses * or &, the changes occurring inside the function will remain permanent. Example: + Show Spoiler +
That code works like you would expect it to. myAwesomeInt prints out as 1. However, for C++ classes, this is not the case. If you supply to a function a pointer to an object, the changes made to that object get reverted once you exit the function. To make matters more confusing, STRUCTS in C work exactly you would expect them to. In that regard, C++ is inconsistent. I can bag on C++ all day, but hopefully you guys can see how stupid this is. Topple on the confusion of many inexperienced programmers thinking that strings are primitive types, and you've got a very shitty starting programming experience. Working C code for C "classes": + Show Spoiler +
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cowsrule
United States80 Posts
On November 15 2012 17:46 Abductedonut wrote: HAHAHAHA, I knew someone would eventually run into this problem. C++ is the most trash language in the history of trash languages, and now I shall show you why. Observe: Code #1: + Show Spoiler +
Results: + Show Spoiler + Pointer to kitty: 75F59E34 Address of kitty: 0028FF44 Entered function! Address of kitty: 0028FF20 Pointer to kitty: 75F59E34 Modified Code #2: + Show Spoiler +
Results: + Show Spoiler + Address of kitty: 0028FF44 Entered function! Address of kitty: 0028FF44 Thehehehe. Can you figure out what went wrong! Ruh roh! Care to elaborate on why those examples demonstrate the language is crap? I'd be interested in hearing that perspective based around the existence of pointers and references. | ||
Tobberoth
Sweden6375 Posts
On November 15 2012 02:43 white_horse wrote: How hard is it to learn SQL, PHP, C# after you learn C++? I'm an intermediate c++ programmer. It looks like it would be easier since you know a little bit about programming already. I would think a C++ programmer would have no problem learning PHP and C#, though they might write bad code in those languages because the way you code in C++ compared to PHP and C# is very different. SQL is a different story though since it isn't a programming language, and you have to think completely differently when writing SQL than when writing programs. For example, using loops etc is generally a bad idea in SQL, but if you come from a programming background, constructs such as loops might come to you more easily than the query solutions (which are far simpler and faster if you know them). | ||
Abductedonut
United States324 Posts
On November 15 2012 17:59 cowsrule wrote: Care to elaborate on why those examples demonstrate the language is crap? I'd be interested in hearing that perspective based around the existence of pointers and references. Sure! I updated my post actually explaining the error instead of letting people figure it out for themselves for the newer programmers who come to this thread looking for advice/etc. Basically the idea is this. When you're learning C++ from the beginning, you're told that passing by reference (the &) for primitive types (int/char/float/double) is one way to make sure that you do not pass a copy of the variable to a function. That way, changes inside that function will actually change the variable permanently. Later on, you're introduced to pointers (the *) and you're told that passing by reference is really just pointers "in the background." And if you pass pointers (again, the *) of primitive types to a function, then the changes remain permanent. Now objects come along. Well, if I pass to a function a pointer to an object, shouldn't the changes I make to the object be permanent? That only makes sense, since passing pointers to primitives types made the changes permanent. However, that's not the case. Passing a pointer of an object passes that pointer by value (which does not even make sense). To make matters worse, structs are treated differently. So C++ in inconsistent in that sense. Why are my pointers to my objects being passed by value? Once you learn that, you "know" how to get around it but it still does not make logical sense. With C - C "classes" and primitive types are all treated the same way. You pass a pointer to a "class" or a primitive type, the changes are permanent. | ||
mxw
Germany1 Post
On November 15 2012 17:46 Abductedonut wrote: ... There's no argueing about C++ being confusing, but in my opinion this makes it interesting and challenging. There are so many ways of doing stuff with slight distinctions being a huge deal. C++ was my first language, together with Visual Studio, a vast amount of libraries and ASM I think it's the most powerful tool. Powerful yet time intensive. At university we have to use Java and it's no doubt useful to have your code being able to run everywhere but when coding the exercises it feels like my hands are tight. | ||
Tobberoth
Sweden6375 Posts
On November 15 2012 18:33 Abductedonut wrote: Sure! I updated my post actually explaining the error instead of letting people figure it out for themselves for the newer programmers who come to this thread looking for advice/etc. Basically the idea is this. When you're learning C++ from the beginning, you're told that passing by reference (the &) for primitive types (int/char/float/double) is one way to make sure that you do not pass a copy of the variable to a function. That way, changes inside that function will actually change the variable permanently. Later on, you're introduced to pointers (the *) and you're told that passing by reference is really just pointers "in the background." And if you pass pointers (again, the *) of primitive types to a function, then the changes remain permanent. Now objects come along. Well, if I pass to a function a pointer to an object, shouldn't the changes I make to the object be permanent? That only makes sense, since passing pointers to primitives types made the changes permanent. However, that's not the case. Passing a pointer of an object passes that pointer by value (which does not even make sense). To make matters worse, structs are treated differently. So C++ in inconsistent in that sense. Why are my pointers to my objects being passed by value? Once you learn that, you "know" how to get around it but it still does not make logical sense. With C - C "classes" and primitive types are all treated the same way. You pass a pointer to a "class" or a primitive type, the changes are permanent. Wait, are you saying objects are passed by value by default in C++? (I haven't programmed C++ in a very long time). It seems to be logical that if you pass an object to a function, you would pass the pointer by value but that would be the same as passing the "object" by reference, so changes should be permanent. It seems weird to me that C++ would copy the whole object by default, just because a pointer to the object was sent by value (especially since it doesn't work like that in C#). | ||
heishe
Germany2284 Posts
On November 15 2012 18:50 Tobberoth wrote: Wait, are you saying objects are passed by value by default in C++? (I haven't programmed C++ in a very long time). It seems to be logical that if you pass an object to a function, you would pass the pointer by value but that would be the same as passing the "object" by reference, so changes should be permanent. It seems weird to me that C++ would copy the whole object by default, just because a pointer to the object was sent by value (especially since it doesn't work like that in C#). No, he just doesn't understand how C++ works. The things he complains about make perfect sense and follow some very simple consistent rules. The behavior when passing references in C++ is exactly the same as passing references in most other languages. And pointers are just references that you can change. | ||
Abductedonut
United States324 Posts
On November 15 2012 18:50 Tobberoth wrote: Wait, are you saying objects are passed by value by default in C++? (I haven't programmed C++ in a very long time). It seems to be logical that if you pass an object to a function, you would pass the pointer by value but that would be the same as passing the "object" by reference, so changes should be permanent. It seems weird to me that C++ would copy the whole object by default, just because a pointer to the object was sent by value (especially since it doesn't work like that in C#). No, that's not what I'm saying. Look, the POINTER ITSELF is passed by value. So modifications to the POINTER ( if the pointer is pointing to the object that originally called the function, changes WILL remain permanent in the object ). However, any changes made to the pointer will not be changed. Let me provide an example. Example: + Show Spoiler +
Note in this case.. kittySize WILL BE PRINTED AS 0! Because we changed the VALUE of the pointer, any changes made to the pointers contents were discarded. Do you see how confusing this can get? *edit* Going to bed for now... I could see how my other post is confusing. No, the changes to the object itself are preserved if you DO NOT modify the value of the pointer. But any changes made to the pointer are discarded because the pointer itself is being passed by value Also, to the poster above me... thanks. I obviously don't know C++ when I pointed out the mistake of the original guy I quoted and proceeded to explain stuff to others. It's pretty easy to come in here and say "he doesn't know what he's talking about." If you're so great at C++ why don't you explain things? | ||
Schokomuesli
Germany12 Posts
C++ definitely has some major flaws (for one: it's way too big, especially considering C++11) but this is not one of them. | ||
mcc
Czech Republic4646 Posts
On November 15 2012 18:33 Abductedonut wrote: Sure! I updated my post actually explaining the error instead of letting people figure it out for themselves for the newer programmers who come to this thread looking for advice/etc. Basically the idea is this. When you're learning C++ from the beginning, you're told that passing by reference (the &) for primitive types (int/char/float/double) is one way to make sure that you do not pass a copy of the variable to a function. That way, changes inside that function will actually change the variable permanently. Later on, you're introduced to pointers (the *) and you're told that passing by reference is really just pointers "in the background." And if you pass pointers (again, the *) of primitive types to a function, then the changes remain permanent. Now objects come along. Well, if I pass to a function a pointer to an object, shouldn't the changes I make to the object be permanent? That only makes sense, since passing pointers to primitives types made the changes permanent. However, that's not the case. Passing a pointer of an object passes that pointer by value (which does not even make sense). To make matters worse, structs are treated differently. So C++ in inconsistent in that sense. Why are my pointers to my objects being passed by value? Once you learn that, you "know" how to get around it but it still does not make logical sense. With C - C "classes" and primitive types are all treated the same way. You pass a pointer to a "class" or a primitive type, the changes are permanent. It makes complete sense if you know what it actually means. Of course the pointer to an object is passed by vlaue, that is completely consistent with how primitive types are passed by reference. func(X *bla) means that pointer is passed to a function by value no matter what X is. And changes to the dereferenced object are permanent in case of primitive types and classes. What you cannot change is the pointer itself, but again that is completely consistent. So you cannot do inside the function : bla = new X(); and expect the change to be permanent as you are trying to change the pointer. If X is int, you also cannot do: int y = 2; bla = &y; and expect it to be permanent. But you can do *bla = 1 or in case of X being a class bla->property = 1; and the changes will be permanent. C++ has some ugly aspects, but what you are saying is not one of them. | ||
mcc
Czech Republic4646 Posts
On November 15 2012 19:15 Abductedonut wrote: No, that's not what I'm saying. Look, the POINTER ITSELF is passed by value. So modifications to the POINTER ( if the pointer is pointing to the object that originally called the function, changes WILL remain permanent in the object ). However, any changes made to the pointer will not be changed. Let me provide an example. Example: + Show Spoiler +
Note in this case.. kittySize WILL BE PRINTED AS 0! Because we changed the VALUE of the pointer, any changes made to the pointers contents were discarded. Do you see how confusing this can get? *edit* Going to bed for now... I could see how my other post is confusing. No, the changes to the object itself are preserved if you DO NOT modify the value of the pointer. But any changes made to the pointer are discarded because the pointer itself is being passed by value Also, to the poster above me... thanks. I obviously don't know C++ when I pointed out the mistake of the original guy I quoted and proceeded to explain stuff to others. It's pretty easy to come in here and say "he doesn't know what he's talking about." If you're so great at C++ why don't you explain things? Actually no, he is correct, you do not know how C++ works, or specifically you have rather bad understanding of pointers in general if that is what is confusing you, as that part of C++ is perfectly consistent and works exactly as one would expect if you understand how pointers work. EDIT: and to explain things. The rules are simple : a) if you pass by value, no changes whatsoever to the parameters are permanent : so class x = new class(); int y = 5; and after f(x,y) is called no changes done in the function are retained. b) if you pass by reference, changes to the memory pointed by the reference are permanent (except if you use const modifier), but any changes done to the pointer (reference) are discarded. So class *x = new class(); int *y; *y = 5; , now if you inside f(x,y) do x->prop = 5; and *y = 6; changes will be retained. If you do x = new class(); and y = &some_int; changes will not be retained as you are trying to change the pointer and that is passed by value. That is basically all, the rules are consistent and nearly everything can be deduced from it. But of course there is a way to retain the changes as you can pass the pointer by pointer. You can have function f(class **x) now if you do class *y = new class(); f(&x) and in f you do *x = new class(), change to the pointer to the class will be retained. | ||
Mstring
Australia510 Posts
On November 15 2012 19:15 Abductedonut wrote: No, that's not what I'm saying. Look, the POINTER ITSELF is passed by value. So modifications to the POINTER ( if the pointer is pointing to the object that originally called the function, changes WILL remain permanent in the object ). However, any changes made to the pointer will not be changed. Let me provide an example. Example: + Show Spoiler +
Note in this case.. kittySize WILL BE PRINTED AS 0! Because we changed the VALUE of the pointer, any changes made to the pointers contents were discarded. Do you see how confusing this can get? *shrugs*. All the examples you've shown so far displayed as I expected. If I dived into a post-box and messed with the addresses, I wouldn't expect the intended recipients to receive the correct letters. It's only confusing if you know that someone dives into your post-box to change the addresses but you still advertise that they're guaranteed to arrive correctly If you really want to modify your pointer you can always pass by reference to pointer:
You can be as indirect as you dare! I think this falls under the category of "blow your foot off" in the old C vs C++ saying... xD | ||
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