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Using member functions of referenced vector C++


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#1 NewVoxel   Members   -  Reputation: 361

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Posted 13 April 2014 - 11:34 PM

I'm having trouble understanding why I can't access the member functions of a vector that I've referenced into a function. I'm trying to overide the << operator for a class I've made that is meant to hold some card objects.

 

Deck.h

#ifndef _deck_h
#define _deck_h
#include "card.h"
#include <vector>

/// This class provides several functions for creating and handling a deck of cards.

using namespace std;

class Deck
{
public:

    /// \brief
    ///
    /// No Argument constructor – Creates a dynamic array of Card objects and initialises them. Initialises cardsDealt to 0.
    ///
    Deck();

    /// \brief
    ///
    /// Destructor – deletes the dynamic array
    ///
    ~Deck();

    /// \brief
    ///
    /// Gets the next card from the deck
    ///
    /// \return Card - AD, 9S, ... etc
    ///
    Card dealNextCard();

    /// \brief
    ///
    /// Shuffles the cards in the deck
    ///
    void shuffle();

    /// \brief
    ///
    /// Sends a string representation of the cards in the deck to the output stream.
    ///
    friend ostream& operator<<(ostream& out, Deck& deck);

private:
    vector<Card> deck;
    int cardsDealt;
};


#endif // _deck_h

Deck.cpp

#include "deck.h"
#include "card.h"
#include <iostream>
#include <algorithm>

//Creates a dynamic array of Card objects and initialises them. Initialises cardsDealt to 0.
Deck::Deck()
{
    cardsDealt = 0;
    for(int suits = CLUBS; suits <= SPADES; suits++)
    {
        for(int ranks = TWO; ranks <= ACE; ranks++)
        {
            deck.push_back(Card(static_cast<Rank>(ranks), static_cast<Suit>(suits)));
        }
    }
}

//Destructor
Deck::~Deck()
{
    //~No objects to be deleted
}

//Gets the next card from the deck
Card Deck::dealNextCard()
{
    Card cardDealt = deck.back();
    deck.pop_back();
    return cardDealt;
}

//Shuffles the cards in the deck
void Deck::shuffle()
{
    random_shuffle(deck.begin(), deck.end());
}

//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, Deck& deck)
{
    deck.begin();
}

main.cpp

/*
 * File: shuffle.cpp
 * Creates a deck of cards, shuffles them and displays them.
 */

#include <iostream>
#include <iomanip>

#include "deck.h"

using namespace std;

int main() {

	Deck deck;
	cout << deck << endl << endl;

	deck.shuffle();
    cout << deck << endl << endl;

	return 0;
}


The problem occurs at the bottom of my Deck.cpp file. When the program is run it gives me "error 'class Deck' has no member named 'begin'" Which is true that it doesn't, but I thought I was passing in a reference to the vector<Card> deck variable that I make in the Decks constructor which does have access to all of the vectors functions as you can imagine.

 

So is the only way I can get the functionality of a vector in my reference to copy the functions over into my Deck class like so:

Card Deck::getLastCard()
{
    return deck.back();
}

for every method or is there a simpler way. All I want to do is iterate over the cards in the Deck and present them on screen but this minor reference has stopped me dead in my tracks.


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#2 NewVoxel   Members   -  Reputation: 361

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Posted 13 April 2014 - 11:45 PM

Well I'm an idiot. Turns out all I had to do was reference the deck inside my reference to gain access to the functions.

ostream& operator<<(ostream& out, Deck& deck)
{
    deck.deck.begin();
}

I'll remind myself not to use stupid names again.


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#3 phil_t   Crossbones+   -  Reputation: 4096

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Posted 13 April 2014 - 11:46 PM

I think you're confused because you named a member variable with the same name as your class (and input parameter).

 

Look, you have:

//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, Deck& deck)
{
    deck.begin();
}

You probably want:

//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, Deck& deck)
{
    deck.deck.begin();
}

Or better yet, rename 

vector<Card> deck;

to

vector<Card> cards;

and use

//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, Deck& deck)
{
    deck.cards.begin();
}


#4 NewVoxel   Members   -  Reputation: 361

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Posted 13 April 2014 - 11:50 PM

 

I think you're confused because you named a member variable with the same name as your class (and input parameter).

 

Look, you have:

//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, Deck& deck)
{
    deck.begin();
}

You probably want:

//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, Deck& deck)
{
    deck.deck.begin();
}

Ha yeah thanks just figured it out. Helps a lot to step back and try to explain what's going on. Got rid of the tunnel vision I've had for the past hour or so.


Your authority is not recognized in Fort Kick-ass http://www.newvoxel.com


#5 ChaosEngine   Crossbones+   -  Reputation: 2499

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Posted 14 April 2014 - 06:15 AM

NewVoxel, you actually don't need a destructor for your deck class. The vector will clean up after itself.
 
Also for your stream operator, you probably want a const reference
//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, const Deck& deck)
{
    for (Card &c : deck.deck)
    {
        out << c << ' ';
    }
    return out;
}
If you think clients of the Deck class will need to iterate over the deck, you may want to provide begin and end forwarding functions.

Finally, when you initialise your class, you may as well initialise your vector since you know the size.
//Creates a dynamic array of Card objects and initialises them. Initialises cardsDealt to 0.
Deck::Deck()
  : cardsDealt(0)
  , deck(52)
{
    int count = 0;
    for(int suits = CLUBS; suits <= SPADES; suits++)
    {
        for(int ranks = TWO; ranks <= ACE; ranks++)
        {
            deck[count++] = Card(static_cast<Rank>(ranks), static_cast<Suit>(suits));
        }
    }
} 

Edited by ChaosEngine, 14 April 2014 - 06:15 AM.

if you think programming is like sex, you probably haven't done much of either.-------------- - capn_midnight

#6 Álvaro   Crossbones+   -  Reputation: 13923

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Posted 14 April 2014 - 09:53 AM

I have one observation that is only marginally relevant: If you need your deck class to be really fast (for instance if you are writing an AI that uses Monte Carlo methods), you can represent a deck or a hand in a 64-bit integer, and many operations are made faster as a result.

 

Dealing a random card is actually one of the harder things to do with the "bitboard" representation: You need to use fancy instructions from the BMI2 instruction set to make it efficient, and this is only available in very recent processors.

 

But if you want to do things like evaluating a poker hand, bitboard is the way to go.

 

What game is it you are implementing?



#7 NewVoxel   Members   -  Reputation: 361

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Posted 16 April 2014 - 01:23 AM


NewVoxel, you actually don't need a destructor for your deck class. The vector will clean up after itself.

 

Probably should remove that. Bad habbit I've gotten into putting them in everything.

 


Also for your stream operator, you probably want a const reference

 

Guessing it's common practice to declare everything that won't be changed. Don't suppose I should put the deck argument in all capitals aswell heh heh.

 


Finally, when you initialise your class, you may as well initialise your vector since you know the size.

 

Thought about doing that but, I'll probably do that by passing in an argument to a seperate constructor as my deck needs to change size for testing.

 


But if you want to do things like evaluating a poker hand, bitboard is the way to go.

What game is it you are implementing?

 

Not sure how this bitboard would be implemented, but I'll look into it. I'm sure what I have at the moment will suffice though. I'm just working on a card game called bridge; I guess it's kind of like uno. Basically up to the logic part now having mostly set up the player hands. I just have to automate the game so all the computers make the right move according to their hands.


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#8 Lantre   Members   -  Reputation: 184

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Posted 19 April 2014 - 06:46 AM

 

 

I think you're confused because you named a member variable with the same name as your class (and input parameter).

 

Look, you have:

//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, Deck& deck)
{
    deck.begin();
}

You probably want:

//Sends a string representation of the cards in the deck to the output stream.
ostream& operator<<(ostream& out, Deck& deck)
{
    deck.deck.begin();
}

Ha yeah thanks just figured it out. Helps a lot to step back and try to explain what's going on. Got rid of the tunnel vision I've had for the past hour or so.

 

 

I find it quite interesting how much clarity you gain from merely explaining the problem to someone else, often the solution pops into your head right there. :)

 

I suppose that is why they say if you really want to master a topic you should try teach it to other people.






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