for_each bind vector of vector resize
This is my first question. I gave up and will use a hand rolled functor for this, but I am curious as to how it is supposed to be done. The contrived example below is intended to resize all of the vectors in a vector to be of size 9, by filling them with nulls. The indicated line causes MinGW GCC 4.5.0 to spew a lot of template errors. I've tried several different permutations, but only posted the code that I consider to be "closest to correct" below. How should it be written? Note, I want to retain the two-argument version of resize.
#include <vector>
using std::vector;
#include <algorithm>
using std::for_each;
#include <tr1/functional>
using std::tr1::bind;
using std::tr1::placeholders::_1;
int main() {
vector<vector<void *> > stacked_vector(20);
for_each(stacked_vector.begin(),stac开发者_StackOverflow社区ked_vector.end(),
bind(&std::vector<void *>::resize,_1,9,0/*NULL*/)); // voluminous error output
return 0;
}
Thank you very much for your input.
It's hard to say without seeing the error output (and frankly, even with it). However, try passing the NULL as a void*
type: static_cast<void*>(0)
. Otherwise the object returned by bind
tries to give an int value as the second parameter to resize
.
Try this.
#include <functional>
#include <algorithm>
#include <iostream>
#include <vector>
int main()
{
typedef std::vector<int> vec_int;
typedef std::vector<vec_int> vec_vec_int;
// Do this to make the _1 work
using namespace std::placeholders;
static const int FIRST_DIM = 5;
static const int SECOND_DIM = 10;
static const int DEFAULT_VALUE = 66;
vec_vec_int v(FIRST_DIM);
std::for_each(v.begin(), v.end(),
std::bind(&vec_int::resize, _1, SECOND_DIM, DEFAULT_VALUE));
std::cout << v[4][9];
return (0);
}
If you do not want to specify the default value, you do not need to.
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