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Join Date: May 2006

Posts: 13

Reputation: achala is an unknown quantity at this point

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achala

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Newbie Poster

lists and vectors

May 21st, 2006

hello,
i have a few questions pls help me out with them coz am really confused ..

1. can lists or vectors passed as parameters in a function?
2. can the lists or vectors be returned ?

i want to use lists or vectors in classes i need to knw if this is possible .
pls help me out
thankx.

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Join Date: Jun 2005

Posts: 1,496

Reputation: WolfPack has a spectacular aura about

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WolfPack

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Mentally Challenged Mod.

Re: lists and vectors

May 21st, 2006

1. can lists or vectors passed as parameters in a function?
Yes
2. can the lists or vectors be returned ?
Yes

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Join Date: Jun 2005

Posts: 2,052

Reputation: Rashakil Fol is just really nice

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Rashakil Fol Rashakil Fol is offline

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Super Senior Demiposter

Re: lists and vectors

May 22nd, 2006

Beware of the performance costs, though. If you just pass a vector, as in the code below, you'll end up copying the entire vector, which takes an amount of time proportional to the length of the vector. Unless the compiler is unreasonably intelligent, which is never the case.

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
int foo(vector<int> x) {
   return x.back() - x.front();
}
int foo(vector<int> x) {
   return x.back() - x.front();
}

So in situations like these, pass the object by reference, so that x refers to caller's vector.

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
int foo(vector<int>& x) {
    return x.back() - x.front();
}
int foo(vector<int>& x) {
    return x.back() - x.front();
}

The second version takes a constant amount of time.

All my posts may be redistributed under the GNU Free Documentation License.

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Join Date: May 2006

Posts: 13

Reputation: achala is an unknown quantity at this point

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achala

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Newbie Poster

Re: lists and vectors

May 23rd, 2006

thankx ... am doing a project for school which involves a lot of file operations i wantedto avoid using an intermediate file as a buffer so thought of using lists/vectors which will be faster and easier .. but the cost overhead is higher but so is using the files so evens it out i think ...
thaknx

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Join Date: Jul 2005

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Reputation: Lerner is a name known to all

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Lerner

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Posting Virtuoso

Re: lists and vectors

May 23rd, 2006

Assuming you have enough memory, passing a list/vector should be faster than file access for the same information. Passing by reference does expose the material being passed to being changed, so remember to use the keyword const judiciously if you don't want that to happen.