Re: What is this function object?

From:
 zhangyw80@yahoo.com.cn
Newsgroups:
comp.lang.c++
Date:
Sun, 04 Nov 2007 22:38:06 -0800
Message-ID:
<1194244686.010394.251950@q5g2000prf.googlegroups.com>
On 11 5 , 1 13 , Porkling <porkl...@yeah.net> wrote:

Here,PrintInt(),is a function object yet.
It runs constructor first (doing nothing here) , and runs operator()
later.

On Mon, 05 Nov 2007 04:58:13 -0000, "webinfin...@gmail.com"

<webinfin...@gmail.com> wrote:

Could anyone explain this snippet for me?

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

class PrintInt {
 public:
     void operator() (int elem) const {
        cout << elem << ' ';
     }
};

int main() {
 vector<int> coll;
 for (int i = 1; i <=9; ++i)
    coll.push_back(i);

 for_each (coll.begin(), coll.end(), PrintInt()); // I don't
understand here
}

for_each needs a function object, so if we are doing: PrintInt p, then
we call for_each(coll.begin(), coll.end(), p()); I will understand,
but what is this "PrintInt()" here? Is it a default constructor? Or
just a call to overloaded operator ()?

Thank you for your response.- -


- -


accurately, opeartor() is called inside for_each, not immediately
after default constructor

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