Learning Vectors

[william_g]

I am using Dev C++ and I am learning about the Standard Template Library so I decide to make a minor function to test my knowledge. I decide to try to erase the prototype and replace it with the function and still has problems. I am wondering if I made some minor mistake or what? Thanks for taking the time to read my post.

code updated.

This is my error log:

8 C:\Users\William\Desktop\book\main.cpp variable or field `RemoveFromVector' declared void 
8 C:\Users\William\Desktop\book\main.cpp missing template arguments before "list" 
8 C:\Users\William\Desktop\book\main.cpp expected primary-expression before "value" 
8 C:\Users\William\Desktop\book\main.cpp initializer expression list treated as compound expression 
 C:\Users\William\Desktop\book\main.cpp In function `int main()': 
24 C:\Users\William\Desktop\book\main.cpp `RemoveFromVector' cannot be used as a function 
24 C:\Users\William\Desktop\book\main.cpp At global scope: 
34 C:\Users\William\Desktop\book\main.cpp variable or field `RemoveFromVector' declared void 
34 C:\Users\William\Desktop\book\main.cpp redefinition of `int RemoveFromVector' 
8 C:\Users\William\Desktop\book\main.cpp `int RemoveFromVector' previously defined here 
34 C:\Users\William\Desktop\book\main.cpp missing template arguments before "list" 
34 C:\Users\William\Desktop\book\main.cpp expected primary-expression before "value" 
35 C:\Users\William\Desktop\book\main.cpp expected `,' or `;' before '{' token 
 C:\Users\William\Desktop\book\Makefile.win [Build Error]  [main.o] Error 1 

#include <iostream>
#include <vector>
#include <algorithm>
#inlclude <string>

using namespace std;

void RemoveFromVector(vector *list, string value);

int main()
{
    
    vector<string>list;
    list.push_back("test");
    list.push_back("will be here afterwards");
    list.push_back("test");
    
    vector<string>::const_iterator iter;
    
    cout << "Here is the vector list: \n";
    for(iter = list.begin(); iter != list.end(); ++iter)
             cout << (*iter) << endl;
    
    RemoveFromVector(list, "test");
    
    cout << "After method: \n";
    for(iter = list.begin(); iter != list.end(); ++iter)
             cout << (*iter) << endl;
             
    system("PAUSE");
    return 0;    
}

void RemoveFromVector(vector *list, string value)
{
     vector<string>::const_iterator iter;
     int x = 0;
     for(iter = list.begin(); iter != list.end(); ++iter)
     {
              if( (*iter) == value )
                  list.erase(list.begin() + x);
              x += 1;
     }                 
}

[Doritos_Man]

Don't use Dev C++

[Lord Ned]

I don't see where you defined X for the record. Please post using [cpp] tags as it'll add line numbers.

[Overv]

You're creating a new vector, not passing the original one by reference. The original vector is never altered.

[william_g]

@Overv
I forgot about that and will add to pass by address and that should allowed the original vector to be altered

@Lord Nerd
I added int x

[Overv]

Let me address your errors.

[cpp]#inlclude <string>[/cpp]

[i]#include[/i] is misspelled, so the compiler will ignore this header and strings cannot be used.

[cpp]using namespace std;[/cpp]

Not an error, but you don't want every function in the standard library in your global namespace.

[cpp]void RemoveFromVector(vector list, string value);[/cpp]

[i]vector[/i] is an incomplete type, you need to specify what type the list should contain as you did later on. Also note that the list is passed as a copy, so can [b]not[/b] be modified by this function.

[cpp]system("PAUSE");[/cpp]

This is Windows specific code and slow. A completely new process has to be started just to pause your program.

[cpp]vector<string>::const_iterator iter;[/cpp]

Why is the iterator not defined in the loop body?

[cpp]x = 0;[/cpp]

[i]x[/i] is both not needed and undefined.

[cpp]if( (*iter) == value )
list.erase(list.begin() + x);[/cpp]

This construction is not necessary, you can just pass the iterator to [i]erase[/i]. You have a problem though, because since vector is a linked list, your iterator will be instantly rendered invalid by calling [i]erase[/i].

My fixed code:

[cpp]#include <iostream>
#include <vector>
#include <algorithm>
#include <string>

using std::vector;
using std::string;
using std::cout;
using std::endl;

void removeFromVector( vector<string>& list, string value );

int main()
{
vector<string> list;
list.push_back( "test" );
list.push_back( "will be here afterwards" );
list.push_back( "test" );

vector<string>::const_iterator iter;

cout << "Here is the vector list:\n";
for ( iter = list.begin(); iter != list.end(); iter++ )
cout << (*iter) << endl;

removeFromVector( list, "test" );

cout << "After method:\n";
for ( iter = list.begin(); iter != list.end(); iter++ )
cout << (*iter) << endl;

std::getchar();
return 0;
}

void removeFromVector( vector<string>& list, string value )
{
for ( vector<string>::const_iterator iter = list.begin(); iter != list.end(); iter++ )
{
if ( (*iter) == value )
{
iter = list.erase( iter );
if ( iter == list.end() ) return;
}
}
}[/cpp]

[william_g]

Thanks for all the help

[Overv]

You can additionally use [i]const string& value[/i] as well to pass the string by reference.