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A convenient untruth: Array notation in C is a lie

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Re: A convenient untruth: Array notation in C is a lie

#21

Post by cessor »

The equivalent in C# always made more sense to me (not comparing memory or allocation model between the languages, but simply syntax in relation to a person reading it):

    int[] arr = new int[5]; // C#

    int arr[5]; // C
The fact that the brackets go on the datatype always made more sense to me, after all, I want to refer to memory of a certain cell size (as indicated by int). I realize that there is a lot of stuff going on when using new, but i believe even in C it should read, because you effectively change the datatype (to be of type pointer, rather than int).

    int[5] arr;
But then, I will now duck and get the hell out. This is the same reason why it feels wrong to write:

    int *arr;
You're not changing the identifier, you're trying to change the datatype.

In summary, I believe that the syntax to fiddling with pointers in C is very misleading, and this I fully agree with the article, but as many people are accustomed to this notation, I will now duck and get far away from the internet, in fear of all the hateful comments explaining to me how I am wrong, and apparently just don't understand the superior beauty of complicated C syntax. I will now go and check my garbage collected privilege.

Re: A convenient untruth: Array notation in C is a lie

#22

Post by baydonFlyer »

anjc wrote: post #2

It's not that convenient an untruth seeing as these are probably some of the first things you learn in C, and some of the first gotchas that'll getcha. Having said that, the article was well written.

I wish that was the case, as in the "first things you learn in C" unfortunately in most cases I come across it's not and many C programmers maybe know that very basics (int* ptr = arr;) but not much beyond that.

Re: A convenient untruth: Array notation in C is a lie

#23

Post by bluetomcat »

cessor wrote: post #21

The equivalent in C# always made more sense to me (not comparing memory or allocation model between the languages, but simply syntax in relation to a person reading it): int[] arr = new int[5]; // C# int arr[5]; // C The fact that the brackets go on the datatype always made more sense to me, after all, I want to refer to memory of a certain cell size (as indicated by int). I realize that there is a lot of stuff going…

> I will now duck and get far away from the internet, in fear of all the hateful comments explaining to me how I am wrong, and apparently just don't understand the superior beauty of complicated C syntax.

I am going to be that person :-)

One phrase – "declarations mirror use". In a declaration, you use the same set of operators around the declared object that you would use in a normal expression. All of these operators (asterisk, `[]` and `()`) have the exact same precedence and associativity as in the rest of the language. The type specifier(s) on the left is the final type of the expression that you get after applying all of the operators in the correct order as per the precedence/associativity rules.

So when you see:

    char *arr[X]
You identify the identifier first: `arr`. Then, because `[]` takes precedence over the asterisk, you say that `arr` is an array (of size X) of pointers to `char`. In other words, the expression `*arr[some_index]` is of type `char`.

Re: A convenient untruth: Array notation in C is a lie

#24

Post by MichaelBurge »

TickleSteve wrote: post #18
MichaelBurge wrote: post #11

I'd be careful about assuming that C code run on a human interpreter behaves similarly to C code compiled by a modern compiler. For example, string literals probably don't actually have to exist in memory anywhere, but could arise implicitly from the control flow of your program. A compiler could probably turn: char *x = "abcdefghijklmnopqrstuvwxyz" printf("%s", x) into something like: for (int x = 'a'; x Maybe when…

You're describing a general problem in general terms... Does a program that has no side effects even exist?? ooOOOoh, spooky.... BTW, yes I know what you're getting at... optimisers are allowed to perform any transformation as long as they're semantically equivalent. This applies to all languages.

> This applies to all languages.

Sure, but it's common for C programmers to think C is a low-level language with concepts that map straightforwardly to the target machine. You can't simultaneously think that C is a low-level language "close to the machine" and that your program can be freely rewritten into an eldritch horror. That's the only reason it would be a good "lie".

Contrast that with something like Perl, where people accept that an array is whatever Larry Wall wants it to be.

Re: A convenient untruth: Array notation in C is a lie

#25

Post by burntsushi »

jcoffland wrote: post #7

I suppose this article is tongue-in-cheek but it doesn't really demonstrate lies in the C language. It does point out some of the quirks of arrays in C but not calling them real arrays is a matter of interpretation of terms. C defined what the term array meant for a lot of the languages that followed it. That today's languages have diverged from C's definition of array is not surprising.

From the OP:

> Of course, if you’ve read this far you’ll (hopefully) realise that this post should have been taken in jest. Arrays aren’t really a lie (any more than any of C’s constructs are). Despite all the ‘trickery’ C’s arrays work well for many, many programming tasks. They are – as the title of this article suggests – a very convenient set of untruths.

Re: A convenient untruth: Array notation in C is a lie

#26

Post by posterboy »

cessor wrote: post #21

The equivalent in C# always made more sense to me (not comparing memory or allocation model between the languages, but simply syntax in relation to a person reading it): int[] arr = new int[5]; // C# int arr[5]; // C The fact that the brackets go on the datatype always made more sense to me, after all, I want to refer to memory of a certain cell size (as indicated by int). I realize that there is a lot of stuff going…

Java also gets this right, probably in direct response to the crufty C syntax.

> (to be of type pointer, rather than int)

No,the array typeis not a pointer, although implicit casts to pointer occur e.g. for passing arrays as function arguments. The practical difference is ... well, I don't know.

Re: A convenient untruth: Array notation in C is a lie

#27

Post by logicallee »

spacelizard wrote: post #8

Brings back fond memories of the first time I learned C, when I really had to dig into what the difference was between storage durations (auto/stack, dynamic/heap, static, thread local). It makes it increasingly important to think about when an object is going to be stored, and for how long. To me this is still a really useful concept that most high-level languages seem to have all disregarded in favor of extremely e…

>Brings back fond memories of the first time I learned C, when I really had to dig into what the difference was between storage durations (auto/stack, dynamic/heap, static, thread local)

If those are your fond memories, I'd hate to hear your traumatic ones. :P

Re: A convenient untruth: Array notation in C is a lie

#28

Post by TickleSteve »

dagw wrote: post #16
coldtea wrote: post #13

Earlier quoted context omitted.

Four answers: No, C (and C++) is used as much as ever. HN echo chamber aside, Rust and/or Go haven't made much of a dent. No, we had such articles for decades. No, it's just an article that points some issues with C, like exist for every language and environment (e.g. tons of articles on JS shortcomings). No correlation whatsoever with such an article and the language falling out of mainstream use. No, this is a biza…

No, C (and C++) is used as much as ever Is this really true, especially for C? Lots of things that used to be done in C is today done in C++ and lots of things that used to be done in C++ is today done in Java or C#.

In the embedded world, the default language is still C by a wide margin. You have to argue hard to have C++ considered and languages like Rust&Go just aren't on the radar.

Only in HN world is C considered legacy. For the rest of the world, its the well-known workhorse of the software world.

Re: A convenient untruth: Array notation in C is a lie

#29

Post by mannykannot »

bluetomcat wrote: post #23
cessor wrote: post #21

The equivalent in C# always made more sense to me (not comparing memory or allocation model between the languages, but simply syntax in relation to a person reading it): int[] arr = new int[5]; // C# int arr[5]; // C The fact that the brackets go on the datatype always made more sense to me, after all, I want to refer to memory of a certain cell size (as indicated by int). I realize that there is a lot of stuff going…

> I will now duck and get far away from the internet, in fear of all the hateful comments explaining to me how I am wrong, and apparently just don't understand the superior beauty of complicated C syntax. I am going to be that person :-) One phrase – "declarations mirror use". In a declaration, you use the same set of operators around the declared object that you would use in a normal expression. All of these operato…

To be fair, while declaration mirrors use, the use contains a few traps for the beginner.

If you have written some assembler, you will see where C is coming from. It just occurred to me that most early C programmers were probably proficient In assembly.

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