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C++ vectors problem

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Join Date: Sep 2008

Posts: 10

Reputation: mugun has a little shameless behaviour in the past

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mugun

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Newbie Poster

C++ vectors problem

-1

Oct 5th, 2008

hello everyone....i need some help,i am using c++ and vectors, and text files to create a library system and i have a problem.....i used a vector named v1 and i was trying to use an if else to assign a created vectors elements value to another value

example like v[10] is "Storybook5"
i tried this v[10]="storybook3"
and this also v.at(10)="storybook3"

it still will not change,it ll come out Storybook5

i need help.....this is my code.....

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
void LibraryMember::PrintLoanMem()//this is to print the members on loan,and reduce repetition of members
{
v1.clear();
ifstream loanfile("loan.txt");
string info;
int i;
int j;
int count=0;
int count2=0;
if (loanfile.is_open())
{
while(!loanfile.eof())
{
	getline(loanfile,info);
	v1.push_back(info);
count++;
}
}
count2=count;
v1[3]="";
for(i=0;i<count;i++)
{
for(j=0;j<count2;j++)
{
if (v1[j]==v1[i])
{
v1[j]=="";	
}
}
}
ofstream out("loanMem.txt",ios::app);
size_t size = v1.size();
for (size_t i = 0; i < size; i++) 
{
if(v1.at(i)=="")
{
}
else
out << v1[i] <<endl;
}
}//end function printloan mem
void LibraryMember::PrintLoanMem()//this is to print the members on loan,and reduce repetition of members
{
v1.clear();
ifstream loanfile("loan.txt");
string info;
int i;
int j;
int count=0;
int count2=0;
if (loanfile.is_open())
{
while(!loanfile.eof())
{
	getline(loanfile,info);
	v1.push_back(info);
count++;
}
}
count2=count;
v1[3]="";
for(i=0;i<count;i++)
{
for(j=0;j<count2;j++)
{
if (v1[j]==v1[i])
{
v1[j]=="";	
}
}
}
ofstream out("loanMem.txt",ios::app);
size_t size = v1.size();
for (size_t i = 0; i < size; i++) 
{
if(v1.at(i)=="")
{
}
else
out << v1[i] <<endl;
}
}//end function printloan mem

Last edited by Ancient Dragon; Oct 5th, 2008 at 6:42 am. Reason: add code tags

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Join Date: Sep 2008

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Sci@phy

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Re: C++ vectors problem

Oct 5th, 2008

I'd appreciate some more code

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Join Date: Aug 2008

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grumpier

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Posting Whiz in Training

Re: C++ vectors problem

Oct 5th, 2008

More specifically, a small piece of code that actually exhibits the behaviour you consider to be a problem.

The code you've given does not appear related to the text in your post in any way.

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Join Date: Apr 2008

Posts: 670

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Freaky_Chris Freaky_Chris is offline

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Practically a Master Poster

Re: C++ vectors problem

Oct 5th, 2008

Indeed, however i have a feeling it may be a similar problem to this....

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
if (v1[j]==v1[i])
{
v1[j]=="";	
}
if (v1[j]==v1[i])
{
v1[j]=="";	
}

What exactly does this do?

Knowledge is power -- But experience is everything

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Join Date: Jul 2008

Posts: 2,001

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ArkM

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Postaholic

Re: C++ vectors problem

Oct 5th, 2008

I think it's a problem with your understanding of the std::vector class properties.
Before using v[10] you must initialize v[10] vector element. For example, you can declare std::vector<type> v(N) or call v.push_back(something) at least N times or call v.resize(N) where N >= 11.