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If I have the following:
void SomeFunction()
{
for(int i=0; i<1000; i++)
{
// Do something
}
}
My question is the variable i redeclared as integer for each successive loop?
Is it best to declare i first for stack purposes..
void SomeFunction()
{
int i;
for( i=0; i<1000; i++)
{
// Do something
}
}
I just thinking about better code execution.
If it were to be declared each successive loop, then your loop would never end cuz the value would always be reset :p
it's kinda preference, really. If it's a small function, I'll often times declare it in the for loop. For larger functions, though, where I (may) have more than one loop and would want to re-use the i variable, I declare it at the top of the function with all my other variables
No it is not redeclared. Only diference that comes to my mind is that (1) will be visible only in the scope of the loop (in VS.NET) in VC6 it will be visible in and after the loop. :wave:
This is not true for the version of VC++.Net that I have (7.1).Quote:
Originally posted by Mr. Tomaszek
Only diference that comes to my mind is that (1) will be visible only in the scope of the loop (in VS.NET) in VC6 it will be visible in and after the loop.
This compiles fine.Code:for (int i=0; i<10; i++) {
}
for (i=0; i<10; i++) {
}
I believe this is in violation of the ANSI spec though.
//NOT RELATED TO THE ORIGINAL QUESTION
It is definitely an annoyance
just limit the scope
Code:{
for (int i=0; i<10; i++)
{
}
}
{
for (int i=0; i<10; i++)
{
}
}
That would be expected since the inner loop is in the scope of the outer. Where VC deviates from the spec is i is still visible following the outer loop (in your example). It should only exist in the scope of the for loop in which it's declared.Quote:
Originally posted by wayside
This is not true for the version of VC++.Net that I have (7.1).
This compiles fine.Code:for (int i=0; i<10; i++) {
}
for (i=0; i<10; i++) {
}
I believe this is in violation of the ANSI spec though.
There are no inner or outer loops in this example. If it were, you'd be in trouble modifying loop counter of the outer loop in the inner loop.Quote:
Originally posted by GCDEF
That would be expected since the inner loop is in the scope of the outer. Where VC deviates from the spec is i is still visible following the outer loop (in your example). It should only exist in the scope of the for loop in which it's declared.
ANSI states that the scope of loop variable (declared in the for() statement) is a body of that loop. MS maintains non-standard implementation for backward compatibility with the software already written in non-standard way. There is a compiler switch that makes current Visual C++ compilers compliant with ANSI.
Ah.. didn't know there was a switch. good info
It would be /Za (or disable lanquage extensions in the project settings)
Right.
Or, you could specify it like that (MSDN):
Quote:
/Zc:forScope (Force Conformance in for Loop Scope)
Use /Zc:forScope if you want standard C++ behavior for for loops with Microsoft extensions (/Ze).
You're right, I misread the brackets. I always find that style of coding very hard to read.Quote:
Originally posted by VladimirF
There are no inner or outer loops in this example. If it were, you'd be in trouble modifying loop counter of the outer loop in the inner loop.
ANSI states that the scope of loop variable (declared in the for() statement) is a body of that loop. MS maintains non-standard implementation for backward compatibility with the software already written in non-standard way. There is a compiler switch that makes current Visual C++ compilers compliant with ANSI.
The fact that non ISO for loop scoping is the default is disappointing. It will encourage people to continue to write non-standard code.
There is a workaround to the for scope problem for VC6 - it limits the scope of variables declared in the for statement to the scope of the loop:
#define for if (0) {} else for
Adrian
Hehe, I agree with you, but my company's coding standards specify this bracket style, so I've gotten used to it.Quote:
Originally posted by GCDEF
You're right, I misread the brackets. I always find that style of coding very hard to read.
IT IS BETTER TO DECLARE THE VARIABLE INITIALLY.
WHY???Quote:
Originally posted by S.DARWIN
IT IS BETTER TO DECLARE THE VARIABLE INITIALLY.
I think we're beating this one to death. I think the thread starter got his answer and has disappeared by now, hehe
Anyway, the rules have been explained, it's been explained when/where/how/why different methods are used, how to modify the settings to be more ANSI compliant, and what happens under the most recent MSVS compiler.
I guess the only thing left is a group hug and then its off to new threads!:wave:
CERTAINLY NOT.Quote:
Originally posted by S.DARWIN
IT IS BETTER TO DECLARE THE VARIABLE INITIALLY.
In C++ it is always better to declare a variable as close as possible to the point of first use for the simple reason that you don't want to call a constructor (and later call a destructor) if it's not necessary.
While in some of these simple examples it isn't going to matter (an int's constructor is trivial and there is nothing else between the declaration and the for, so the int gets constructed whichever way you do it), it is good practice not to declare things until you need them. One day your constructor is going to cost you time!
F
I disagree - that's a performance consideration at the expense of readability and hence maintainability.
It's a personal/business/application choice. There are pro's and con's to both.
T
What else can be said about declaration in for loop ? :D
Can the moderators change the title of this topic? Pretty weird to have 20 answers for a Simple question on a For Loop
I wonder if this was an Ammazingly difficult question on a For Loop?
:D
The question was simple enough :p.
No but we can close the thread since it's running into the land of off-topicness (that's from 7th century mickalise)Quote:
Originally posted by PadexArt
Can the moderators change the title of this topic? Pretty weird to have 20 answers for a Simple question on a For Loop
I wonder if this was an Ammazingly difficult question on a For Loop?
:D