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cozzie

Unity if statement in for loop, brackets needed?

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cozzie    5029

Hi,

 

Just a simple question, with a nice opportunity to clean my code :)

I'm not sure when I need to use brackets in a for loop, depending on the code that needs to be executed for each iteration.

 

Example, I have:

 

for(mat=0;mat<mNrMaterials;++mat) 
{	
	if(materials[mat]) ++mEffect[fx].nrMaterials; 
}

Would the result be the same if I use:

 

for(mat=0;mat<mNrMaterials;++mat) 
	if(materials[mat]) ++mEffect[fx].nrMaterials; 

I know that I can leave the brackets out if I just have one line of code for each iteration, like:

 

for(int i=0;i<5;++i)
  something[i] = i*2;

Anyone?

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alvaro    21246
My taste on this has evolved over the years, but I have settled on using curly braces when there is more than one line in the body, even if it is technically only one thing.
for (int mat=0; mat<mNrMaterials; ++mat) {
  if (materials[mat])
    ++mEffect[fx].nrMaterials; 
}

if (foo) {
  if (bar)
    actionA();
  else
    actionB();
}

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Wyrframe    2426

I use unbraced forks only for if-wrapped return, continue, break, and throw statements, because those don't have "else" forks; any subsequent code is an "else" after that.

 

But, I also tend to write very dense loops, frequently without an actual body, so sometimes the body of my loops ends up being a single semicolon, ie

for(int i=0, j=arraylength-1; i<j; array[j--]=array[i++]) ;

 

And that just becomes more unreadable when I waste essentially blank lines putting empty braces on the following couple lines.

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Ectara    3097

I have settled on using curly braces when there is more than one line in the body


I'll throw another vote in this pile. I use no curly braces when the statement does not have its own block scope, and when it can fit cleanly on one line. If it requires two, I put braces on it. Since I put if statements on a separate line from what is executed conditionally, then that means that that is enclosed in braces, too. I do agree that extra braces reduces the possibility of human error; I may consider doing it all the time at a later point. In effect, I use no braces when the block looks concise enough that it can be readily understood as being the sole statement of the block, and that no more statements would be added. If I have to debug, I add braces, output the values, then remove braces when I remove the output code.

In my mind, where I parse the source linearly, a no-brace if statement gives me an explicit measure of what the conditional encompasses, and it looks aesthetically pleasing to my eye at how the simple things appear very obviously simple.

However, once I must team up with someone that is prone to human error in these kinds of places, I'd probably opt to ensure that we aren't each other's downfall.

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SiCrane    11839
My rule for [tt]if[/tt] and brackets is if there is an [tt]else[/tt] then brackets need to go on both halves and an [tt]if[/tt] containing an [tt]if[/tt] or a loop statement requires brackets on the outermost [tt]if[/tt]. So
// fine
if (a) foo;

if (a) if (b) foo; // no good instead do:
if (a) {
  if (b) foo;
}

if (a) for (;;); // also bad, instead:
if (a) {
  for (;;);
}

// fine
if (a) {
  foo;
} else {
  bar;
}
Similarly, for loop statements a loop containing a loop or an if requires brackets.

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Buster2000    4310

My rule is to ALWAYS use braces no matter how little code is inside them.  It is just a more secure way of coding.  There are already resons mentioned above.  But my personal favorite was a senior coder (who was also a complete fuckwit) I worked with a couple of years ago made it a rule that single lines should not have brackets. He also had a list of debug macros that he used.

Instead of disableing the macros when he did a release he just did a grep and replace to comment out all the macros. 

 

So we ended up with:

<get some data>

if(<a problem with data>)  //<commented out macro here>

 

<do processing on the data>
 

 

This pattern by the way he had used in several hundred places throughout the project.  Then he blamed the rest of us for it not working even though we had told him his code was shocking during every single code review.

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wintertime    4108

For me brackets or not seems just like a matter of style. If there are none and you add a second line, surely you should know you also need to add brackets.

But putting the body on the same line as the if is annoying if you happen to want to put a breakpoint there or single step the if, as you cant easily see then if the body was actually run.

Edited by wintertime

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alh420    5995

There is only one case where I feel its acceptable to omit braces.

It's for one line tests with simple expressions like this:

 

if(!some_object) some_object = new SomeClass();

 

If you want to add a second line, you have to start with adding a line break, and at that point, it's very obvious that you need to add brackets too. 

Even with stress levels high.

 

 

For me brackets or not seems just like a matter of style. If there are none and you add a second line, surely you should know you also need to add brackets.

Well, the only protection against idiotic programmers is better hiring and firing decisions. Bracketing conventions won't do.

 

Easy to say until that day you sit there with the deadline looming over your head, with stress levels at max, trying to fix that last show stopper bug.

The "just going to add some print out" happens very easily... And you really dont want to spend even 5 minutes with something like that, totally breaks your flow.

 

Clean and consistent code = less bugs and frustration

always.

Edited by Olof Hedman

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Bregma    9202

I have spent decades coding in C-like languages.  I have seen a significantly disproportionate number of software error arising from not using braces in control statements than from (almost) any other construct.  The 'other construct' is mistaking '=' for '==' in comparisons, but that's less easily avoided.

 

The problem doesn't come from writing new code.  The problem comes from maintaining existing code.  Remember that all code is existing code the moment you're finished typing it.

 

I have worked on projects in which the formalized and enforced coding style dictates that a single line in a control construct should never use braces, likely in an attempt to save on electrons.  With one significant exception, every such project has had a higher bug rate and higher maintenance cost.  The one exception has a very large automated test suite (which takes hours to run) but is under very restricted maintenance, since it's a standard library with strongly defined functionality and wide distribution.

 

There are, of course, strong opinions on the aesthetic of brace usage in coding style.  Such opinions are significantly more important than practical issues such as minimizing maintenance costs or maximizing software reliability.

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alvaro    21246
I have programmed in C-like languages for aboud 20 years now, 13 of them professionally. I have never ever seen a problem with the use of braces. So I don't think it's that important.

It could also depend on what editor you use. Emacs understands the level of indentation you are at, so when you go to add a second line to the `then' clause, the cursor will go to a place where it's obvious that you need braces.

I agree with everyone that the most clear style should be used. So use whatever you think is more clear.

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King Mir    2490

Ho boy, a bracketing convention debate.

 

My advice is to always use braces.

 

In practice, I add braces only when I need them, but don't remove them when the need disappears, such as if debug code is removed or the code is reformatted.

 

Also, I always use a newline after all if statements and non-empty loops. Empty loops get a pair of braces on the same line. 

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Ectara    3097

Empty loops get a pair of braces on the same line.


That's an interesting idea. I use empty braces on the same line for an empty function or class definition. My empty loops look like this:
while(*(src++) = *(dst++))

        ;

 

I guess I just feel like loop bodies should start on the next line, no matter what. I'm also strongly against semi-colon on the same line to prevent things like this:
for(;;);
{
//Why am I not executed as expected?
}

Edited by Ectara

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Buster2000    4310

I have programmed in C-like languages for aboud 20 years now, 13 of them professionally. I have never ever seen a problem with the use of braces.

 

I find that hard to belive that in 13 years of proffesional coding you have never once found a bug written by either you or by someone else that involved incorrect use of braces.

 

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alvaro    21246


I have programmed in C-like languages for aboud 20 years now, 13 of them professionally. I have never ever seen a problem with the use of braces.

 
I find that hard to belive that in 13 years of proffesional coding you have never once found a bug written by either you or by someone else that involved incorrect use of braces.


I'm telling you, I can't remember one. As I said, emacs makes it very obvious if you are writing at the wrong level of indentation. Also, perhaps our testing procedures are good at catching that type of mistake.

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Cornstalks    7030

I have programmed in C-like languages for aboud 20 years now, 13 of them professionally. I have never ever seen a problem with the use of braces. So I don't think it's that important.

I have. Once. (though I've got much less experience than you). It was in the FFmpeg source code. Indentation levels indicated the else statement was part of a different if block, but actual control flow was otherwise. The actual logic ended up being correct, but anyone reading the code was likely to misread the code (like I did initially) because of incorrect indentation levels and a complete lack of braces. That was a fun day.

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wack    1358

I have programmed in C-like languages for aboud 20 years now, 13 of them professionally. I have never ever seen a problem with the use of braces. So I don't think it's that important.It could also depend on what editor you use. Emacs understands the level of indentation you are at, so when you go to add a second line to the `then' clause, the cursor will go to a place where it's obvious that you need braces.I agree with everyone that the most clear style should be used. So use whatever you think is more clear.


I agree with this, after (is it 15 now?) years of coding i have never seen anyone accidentally add code to a statement without braces and failing to add them. Part of it might be because I have mostly worked with coding styles that dictate braces on new lines, and ide/editor support, as you say.

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King Mir    2490

Empty loops get a pair of braces on the same line.


That's an interesting idea. I use empty braces on the same line for an empty function or class definition. My empty loops look like this:
while(*(src++) = *(dst++))

        ;

 

I guess I just feel like loop bodies should start on the next line, no matter what. I'm also strongly against semi-colon on the same line to prevent things like this:
for(;;);
{
//Why am I not executed as expected?
}

It's nice to have the same convention for all blocks, including both functions and loops. And {} is much more noticeable than ;, in part because one doens't normally put {} after a statement otherwise, and in part because it actually means something different for functions, so we're trained to notice it.

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swiftcoder    18432

As I said, emacs makes it very obvious if you are writing at the wrong level of indentation.

To my mind this is 90% of it. If you aren't using an editor that is highly aware of syntax (vim, emacs, sublime, etc), then informal code conventions are going to trip you up.

I really don't know why so many programmers adamantly continue to use inferior tools. For example:
[source]$ g++ -Wall test.cpp[/source]
versus:
[source]$ clang++ test.cpp
test.cpp:5:12: warning: if statement has empty body [-Wempty-body]
if (1 < 2);
          ^
test.cpp:5:12: note: put the semicolon on a separate line to silence this warning[/source]

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Bregma    9202

o my mind this is 90% of it. If you aren't using an editor that is highly aware of syntax (vim, emacs, sublime, etc), then informal code conventions are going to trip you up.

But a syntax-aware editor is not going to catch the valid use of valid syntax.

if (someCondition())
  LOG_DEBUG("after if-statement\n");
  doSomethingBuggy();

Perfectly valid syntax.  Problem is, as is often reported on this forum, the bug goes away in debug mode.

 

Relying on a single tool that works well for writing new code is not a win when you're involved in the 80% of software development called 'maintenance'.  Code is meant to be read, after all, not written, and that includes when looking at diffs during code reviews and online in VCS webviews, where building in a context-sensitive C++ front-end is just not going to cut it.

 

The missing braces after a code change is a common and vexing bug.  I've seen it come up here at gd.net on several occasions.  It's 100% avoidable by always using braces. 

 

Oh, and condemning tools as inferior because you do not know how to use them says less about the tools.

$ cat empty.cpp
int main()
{
  if (1 < 2);
}
 
$ g++ -Wall -Wextra -o empty empty.cpp
empty.cpp: In function ‘int main()’:
empty.cpp:3:13: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]

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swiftcoder    18432

But a syntax-aware editor is not going to catch the valid use of valid syntax.

All of my primary editors fix the incorrect indentation there - it doesn't make the bug go away, but it makes it damn easy to spot during code reviews.
 

Code is meant to be read, after all, not written, and that includes when looking at diffs during code reviews and online in VCS webviews, where building in a context-sensitive C++ front-end is just not going to cut it.

Then auto-format all your code using a pre-checkin hook on your version control.

 

You should probably be doing this anyway, to deal with funky whitespace issues.
 

Oh, and condemning tools as inferior because you do not know how to use them says less about the tools.

The point isn't that I don't know how to use gcc (I do), the problem is that it's off by default, and many users don't know how to turn it on. The whole idea that -Wall does not, in fact, turn on *all* warnings, is a bit of a non sequitur.

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