STL transform algorithm

[jimberger]

hello all,

I am trying to update each value for a set<int> with a integer already defined in the function. I have been trying to use transform algorithm. I can do

void func{
// some stuff which calculates the value of num
int num=10;

transform(set1.begin(),set1.end(),set2.begin(),add)
}

int add(int val)
{
return( val + 2);
}
so this will update every value with 2 and add to set2,but i want to be able to do this by updating each value with &quot;num&quot;
I cant see a way round this. any suggestions?
thanks

 

[Federal102]

You need to use a function object rather than a global function. This is best practice for any kind of STL work.

Someting like this..

class AddNum
{
public:
	AddNum(int);
	int operator()(int);
private:
	int val;
};

//Initialize member value with value of num
AddNum::AddNum(int num)
:val(num)
{}


int AddNum::operator ()(int setVal)
{
	return (setVal + val);
}


int main(int argc, char* argv[])
{
	set<int> set1;
	set<int> set2;

	set1.insert(1);
	set1.insert(2);
	set1.insert(3);

	int num = 10;
	//Note the use of &quot;inserter&quot; below. set2.begin will not work
	transform(set1.begin(), set1.end(), inserter(set2, set2.end()), AddNum(num));

	set<int>::iterator i = set2.begin();
	for(; i != set2.end(); ++i)
		cout << *i << endl;

	return 0;
}