Vector Iteration and Removal in C++

Question

I am trying to iterate over a vector and remove the first occurrence of an object. I keep getting a compile error (using g++), but I am removing it the way stackoverflow answers and other sources suggested removing it. There is probably something super simple that I'm missing, so another set of eyes would be great too.

#include <iostream>
#include <vector>
#include <assert.h>
using namespace std;

bool Garage::remove(const Car &car){
assert(!empty());

int size = v.size();
for(vector<Car>::const_iterator it = v.begin(); it != v.end(); ++it){
    if(it -> Car::make() == car.Car::make()){
        it = v.erase(it);
        assert(v.size() == size - 1);
        return true;
     }
 }
 return false;
}

The compile error is error: no matching function for call to 'std::vector::erase(const Car&)'

Please don't use the homework tag. [It's deprecated.](http://meta.stackexchange.com/questions/147100/the-homework-tag-is-now-officially-deprecated) — chris, Dec 30 '12 at 04:03
The error doesn't seem to match your code. Are you sure your code doesn't say `erase(*it)` or something like that? — Kerrek SB, Dec 30 '12 at 04:04
@chris Sorry, I don't come here often so I didn't realize the tag was no longer used. People used to tell me to add it. — Sams, Dec 30 '12 at 04:05
I did look at the erase/remove algorithm and it seemed like it was for erasing multiple occurrences, but I just want to erase the first occurrence. — Sams, Dec 30 '12 at 04:06
Something simple like `v.erase(std::find(...))` would work. Make sure that it is found, though, before erasing it. — chris, Dec 30 '12 at 04:07
`Car::make()` is static function, so `if(it -> Car::make() == car.Car::make())` will always evaluate to true? — billz, Dec 30 '12 at 04:15

Ryan Guthrie · Answer 1 · 2012-12-30T04:09:30.803

3

You're trying to erase using a const_iterator. Since you're trying to modify the vector, switch to a regular iterator.

for(vector<Car>::iterator it = v.begin(); it != v.end(); ++it){

This works:

int main()
{
   vector<int> ints;

   for (vector<int>::iterator iter = ints.begin();iter != ints.end();++iter)
   {
      ints.erase(iter);
   }
}

This doesn't:

int main()
{
   vector<int> ints;

   for (vector<int>::const_iterator iter = ints.begin();iter != ints.end();++iter)
   {
      ints.erase(iter);
   }
}

Error when using a const_iterator:

test.cpp:18:22: error: no matching function for call to ‘std::vector<int>::erase(std::vector<int>::const_iterator&)’

edited Dec 30 '12 at 04:09

answered Dec 30 '12 at 04:03

Ryan Guthrie

688
3
11

I removed const and it compiles now. Just have to test it a ton. – Sams Dec 30 '12 at 04:10
Just a note that on compilers following the C++11 standard, it *will* work with a `const_iterator`. – Bo Persson Dec 30 '12 at 10:54
1

@Bo Persson With which version of gcc? I am running 4.6.3 (g++ -std=c++0x) and it doesn't support const_iterator. I see where it is specified here, but gcc doesn't support it yet? http://en.cppreference.com/w/cpp/container/vector/erase – Ryan Guthrie Dec 30 '12 at 13:49

score 1 · Answer 2 · edited May 23 '17 at 11:56

1

It appears that you'll need to use find to find the index of the element and subsequently erase it. I say "appears" because I'm not a C++ programmer.

edited May 23 '17 at 11:56

Community

1
1

answered Dec 30 '12 at 04:09

hd1

33,938
5
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Vector Iteration and Removal in C++

2 Answers2