how to sort a vector of object

[Pat Nevin]

hi, Ive a vector of TaxPayer objects, instances of TaxPayer have an instance variable of type float call tax, I want to sort such that it lists the taxpayers in increasing order of how much tax they pay.

i've been trying stuff like
sort (taxpayers.begin(), taxpayers.end());
however this throws up all sorts of errors, as i think this is only applicable to vectors of primitive datatypes....

i.e.

int myints[] = {32,71,12,45,26,80,53,33};
      vector<int> myvector (myints, myints+8); 
      sort (myvector.begin(), myvector.begin()+4);  

so hopefully someone could tell me how to sort a vector of objects based on a member variable...

p.s.

im using pointers when populating my vector dont know if dat makes a dif ie

while (taxStream >> current) {
		//the tax payers wage
		float wage;
		//the tax payers credit
		float credit;

	    taxStream >> wage;
	    taxStream >> credit;

		TaxPayer *t = new TaxPayer(current, wage, credit);
		t->taxAmount();
		t->netPay();
		//And add it to the vector
		taxpayers.push_back(*t);
		pop.add(*t);
		pop.setTax(t->amountDue());
		delete t;

	}//end while() 

thanks

[helios]

The difference is that int already has an implicit sorting algorithm. You need to provide that to std::sort() in order to... sort. You'll probably want to sort based on some kind of ID or by name.

[Pat Nevin]

yeah i already know dat lol, but as asked how do u do it... i want to sort on a member variable of the TaxPayer object called tax of type float... can someone please help lol...

[helios]

Something like this?

struct taxpayersCmp{
	bool operator()(const taxpayer &a,const taxpayer &b) const{
		return a.Float<b.Float;
	}
} taxpayersCmp_;
//...
std::sort(taxpayers.begin(),taxpayers.end(),taxpayersCmp_);

You should have looked closer at the example. There was an example class there, too.

[Pat Nevin]

thanks mate, but example doesnt work for me, think its cus Im using pointers and TaxPayers is a class not a struct....

[helios]

Well, then just change the parameters from references to pointers, and write accessor methods for the member you want to compare.

Duh!

[Pat Nevin]

well sorry, but im only writting in c++ few weeks not used to pointers in java so really haven't a clue how to do that, but would appriciate dearly if u could show me how to....

[helios]

Just replace & with * and . with ->
Simple, isn't it?

[Pat Nevin]

lol im beginning to think its u thats simple my friend....

Im using pointers as stated many times above and not references to memory addresses so im off course already using * and ->.... now if you can only provide vauge unhelpful asides, I rather wait until 2maro when, perhaps I could get some help of someone more european (ie less condescending and actually helpfull) and to the point n less of a know it all without solutions as many americans tend to be......

anyway i sorted by creating/recreating an insertionSort method myself but would of liked to learn how to sort a vector of pointers to objects in C++

[helios]

I meant replace in my example. Why would I tell you to change the references in your program to pointers if I already know you're using pointers?

I hardly think a complete working example (two if you consider that I also gave you the steps on how convert it to pointers which you could have followed had not spent your time misinterpreting my words) qualifies as a "vague unhelpful aside". I should have just posted the link to the std::sort() reference. Would that have been more helpful?

And I'm not American (not even close, really), but we don't take too kindly to this kind of faggotry, around here, either.

[seymore15074]

Post some code. We can be more helpful if we see the declaration of the vector and the class that it is going to contain.

[Pat Nevin]

lol found out meself what was wrong i needed a random access iterator.... thanks seymore...