From: "learning c++" <learning_c@hotmail.com>
To: gcc-help@gcc.gnu.org
Subject: function object, function pointer and function.
Date: Mon, 30 Aug 2004 17:25:00 -0000 [thread overview]
Message-ID: <BAY12-F300yki4jsGvs00011487@hotmail.com> (raw)
Hi, Everyone:
I compiled a short code that invovles function object and function pointer.
in the line: int count1 = count_if(v1.begin(), v1.end(),
&lessThan20Function);
I used the funtion poiter to pass the address of function. It works very
well,
However, when I deleted the symbol "&", it still works. "lessThan20Function"
is the name of function. Can we use the function name as an argument?
What is the advantage of function object?
Thanks in advanace!
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;
bool lessThan20Function(int value)
{
return value < 20;
}
class LessThan20 {
public:
bool operator() (int value) const
{
return value < 20;
}
};
int main() {
int iarr[10] = {2,4,55,6,66,10,22,14,70,1234};
vector<int> v1(iarr, iarr+10);
LessThan20 lt20;
// count_if(start_iterator, end_iterator, predicate);
// Pointer to a function as argument
int count1 = count_if(v1.begin(), v1.end(), &lessThan20Function);
cout << "There are " << count1 << " values less than 20" << endl;
// Function object as argument
int count2 = count_if(v1.begin(), v1.end(), lt20);
cout << "There are " << count2 << " values less than 20" << endl;
return 0;
]
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next reply other threads:[~2004-08-30 17:10 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-30 17:25 learning c++ [this message]
2004-08-30 18:22 ` Eljay Love-Jensen
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