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hrmadhu
Guest
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 Posted: Fri Dec 26, 2003 11:24 pm Post subject: Help on the STL and initializing non-const references with t |
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Hi,
I wish to declare a vector of deque of int, which I do as follows.
#include<vector>
#include<deque>
#include<iostream>
using namespace std;
int main(int argc, char* argv[])
{
int i=1;
int N=0;
while(i<=argc)
{
// parse arguments
// Most importantly extract the value of N
// as
N=atoi(argv[i]);
i++;
}
// some stuff
//declare a vector of deque of int
// vector contains N deque
// each of which are empty initially
// First attempt
vector<deque _MyVariable( N, deque<int>());
// Second Attempt
vector<deque _MyVariable2 (N, deque<int>(0));
// some more stuff
return 0;
}
The compiler cribs
"Warning: should not initialize a non-const reference with a
temporary." in the STL code which is instantiated in the lines of
interest above.
Could someone please clarify the exact effects of initializing in the
above fashion ?
which of the above two attempts should I use ? Is it better not to
initialize the deque i.e. to use
vector<deque _MyVar (N);
?
Thanks In Advance.
Best Regards,
Madhu.
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Jeff Schwab
Guest
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| Posted: Fri Dec 26, 2003 11:37 pm Post subject: Re: Help on the STL and initializing non-const references wi |
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hrmadhu wrote:
| Quote: | Hi,
I wish to declare a vector of deque of int, which I do as follows.
#include<vector
#include
#include
using namespace std;
int main(int argc, char* argv[])
{
int i=1;
int N=0;
while(i<=argc)
{
// parse arguments
// Most importantly extract the value of N
// as
N=atoi(argv[i]);
i++;
}
// some stuff
//declare a vector of deque of int
// vector contains N deque
// each of which are empty initially
// First attempt
vector _MyVariable( N, deque<int>());
|
You're not allowed (in standard C++) to use that name. At least get rid
of the underscore.
| Quote: |
// Second Attempt
vector<deque _MyVariable2 (N, deque<int>(0));
// some more stuff
return 0;
|
You don't need that return statement.
| Quote: | }
The compiler cribs
"Warning: should not initialize a non-const reference with a
temporary." in the STL code which is instantiated in the lines of
interest above.
Could someone please clarify the exact effects of initializing in the
above fashion ?
which of the above two attempts should I use ? Is it better not to
initialize the deque i.e. to use
vector<deque _MyVar (N);
?
|
Yes, IMHO. That's the right way to do it, assuming you change the
variable name.
Good luck,
Jeff
| Quote: | Thanks In Advance.
Best Regards,
Madhu.
|
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|
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hrmadhu
Guest
|
| Posted: Sat Dec 27, 2003 5:13 pm Post subject: Re: Help on the STL and initializing non-const references wi |
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| Quote: | Jeff Schwab <jeffplus (AT) comcast (DOT) net> wrote in message news:
// First attempt
vector<deque _MyVariable( N, deque<int>());
You're not allowed (in standard C++) to use that name. At least get rid
of the underscore.
|
Wow!! I didnt know that. As my coding style, I always prefix all
private and protected members of my classes with _ . Could you please
tell me why and where I can find more on this.
| Quote: |
// Second Attempt
vector<deque _MyVariable2 (N, deque<int>(0));
// some more stuff
return 0;
You don't need that return statement.
|
if I do not put this, then the compiler cribs that main, which is
declared int main(...) does not have a return value. Also, isnt that
the way I return whether the program executed with or without errors ?
return 0 suggests that the program ran successfully, while return -1
says there was an error ?
| Quote: | }
The compiler cribs
"Warning: should not initialize a non-const reference with a
temporary." in the STL code which is instantiated in the lines of
interest above.
Could someone please clarify the exact effects of initializing in the
above fashion ?
which of the above two attempts should I use ? Is it better not to
initialize the deque i.e. to use
vector<deque _MyVar (N);
?
Yes, IMHO. That's the right way to do it, assuming you change the
variable name.
|
if so, can I then simply use the variable as
_MyVar[i].push_back() ?
or do I need to create non-temporary deque<int> and push them back
into the vector one by one ?
Thanks again
Madhu
|
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|
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Jeff Schwab
Guest
|
| Posted: Sat Dec 27, 2003 7:16 pm Post subject: Re: Help on the STL and initializing non-const references wi |
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|
hrmadhu wrote:
| Quote: | Jeff Schwab <jeffplus (AT) comcast (DOT) net> wrote in message news:
// First attempt
vector<deque _MyVariable( N, deque<int>());
You're not allowed (in standard C++) to use that name. At least get rid
of the underscore.
Wow!! I didnt know that. As my coding style, I always prefix all
private and protected members of my classes with _ . Could you please
tell me why and where I can find more on this.
|
TC++PL, p.81:
Names starting with an underscore are reserved for
special facilities in the implementation and the run-
time environment, so such names should not be used in
application programs.
| Quote: | // Second Attempt
vector<deque _MyVariable2 (N, deque<int>(0));
// some more stuff
return 0;
You don't need that return statement.
if I do not put this, then the compiler cribs that main, which is
declared int main(...) does not have a return value.
|
Your compiler is non-standard. In standard C++, the default return
value of main is 0. You are correct to declare it returning an int.
| Quote: | Also, isnt that
the way I return whether the program executed with or without errors ?
return 0 suggests that the program ran successfully, while return -1
says there was an error ?
|
That depends on your system. On Unix, you can return whatever you want,
as long as you document it. There is a sort of gentlemen's agreement
that 0 means success.
| Quote: | }
The compiler cribs
"Warning: should not initialize a non-const reference with a
temporary." in the STL code which is instantiated in the lines of
interest above.
Could someone please clarify the exact effects of initializing in the
above fashion ?
which of the above two attempts should I use ? Is it better not to
initialize the deque i.e. to use
vector<deque _MyVar (N);
?
Yes, IMHO. That's the right way to do it, assuming you change the
variable name.
if so, can I then simply use the variable as
_MyVar[i].push_back() ?
|
Assuming you change the variable name, and 0 <= i < N, yes.
| Quote: | or do I need to create non-temporary deque
into the vector one by one ?
|
No, but you can if you like.
| Quote: | Thanks again
Madhu
|
-Jeff
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hrmadhu
Guest
|
| Posted: Sun Dec 28, 2003 8:17 pm Post subject: Re: Help on the STL and initializing non-const references wi |
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Thanks Jeff. Got it compiling without any error. (in fact it was also
running without error - but I just dislike compiler warnings!!)
Thanks again.
Best Regards,
Madhu.
Jeff Schwab <jeffplus (AT) comcast (DOT) net> wrote
| Quote: | hrmadhu wrote:
Jeff Schwab <jeffplus (AT) comcast (DOT) net> wrote in message news:
// First attempt
vector<deque _MyVariable( N, deque<int>());
You're not allowed (in standard C++) to use that name. At least get rid
of the underscore.
Wow!! I didnt know that. As my coding style, I always prefix all
private and protected members of my classes with _ . Could you please
tell me why and where I can find more on this.
TC++PL, p.81:
Names starting with an underscore are reserved for
special facilities in the implementation and the run-
time environment, so such names should not be used in
application programs.
// Second Attempt
vector<deque _MyVariable2 (N, deque<int>(0));
// some more stuff
return 0;
You don't need that return statement.
if I do not put this, then the compiler cribs that main, which is
declared int main(...) does not have a return value.
Your compiler is non-standard. In standard C++, the default return
value of main is 0. You are correct to declare it returning an int.
Also, isnt that
the way I return whether the program executed with or without errors ?
return 0 suggests that the program ran successfully, while return -1
says there was an error ?
That depends on your system. On Unix, you can return whatever you want,
as long as you document it. There is a sort of gentlemen's agreement
that 0 means success.
}
The compiler cribs
"Warning: should not initialize a non-const reference with a
temporary." in the STL code which is instantiated in the lines of
interest above.
Could someone please clarify the exact effects of initializing in the
above fashion ?
which of the above two attempts should I use ? Is it better not to
initialize the deque i.e. to use
vector<deque _MyVar (N);
?
Yes, IMHO. That's the right way to do it, assuming you change the
variable name.
if so, can I then simply use the variable as
_MyVar[i].push_back() ?
Assuming you change the variable name, and 0 <= i < N, yes.
or do I need to create non-temporary deque
into the vector one by one ?
No, but you can if you like.
Thanks again
Madhu
-Jeff
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