How to change an array with a function?

Question

I'm quite new to C++ and I've ran across a problem.
I'm trying to write a game of Blackjack. I have an array of size 52 of type 'char' with the different cards and I want to shuffle it. I'm not sure how but that's not the problem. I made a function called 'ShuffleDeck' but it doesn't work, says it can't return an array. I can't reference the array either. How should I go about this? Here's the part of code I'm talking about.

void ShuffleDeck(bool &rgCards[]) {
    for (int i = 1; i < 52; ++i) {
        //something
    }
    return rgCards[];
}

All help appreciated.

Luchian Grigore · Accepted Answer · 2012-04-05 21:33:31Z

3

You use a std::vector and shuffle the values in it. Preferably, pass it by reference to the function and work on the original vector.

From your snippet, it's not entirely clear what you expect it to do - you pass an array of bool by reference but return it as an int with the syntax rgCards[] which makes absolutely no sense in that context.

EDIT: As per Fred's comment - you can use random_shuffle.

answered Apr 5, 2012 at 21:33

Luchian Grigore

260k68 gold badges465 silver badges634 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Fred Larson Over a year ago

Or just use random_shuffle() on a std::vector instead of rolling your own shuffle function.

Luchian Grigore Over a year ago

@FredLarson cool, all the stuff in <algorithm> continues to amaze me. :)

argoneus Over a year ago

Yeah well, I didn't really know where I'm going with this but I didn't want not to post any code here. Thanks for the help!

Praetorian · Accepted Answer · 2012-04-05 21:41:55Z

2

From the code snippet you've provided it looks like you're trying to pass a reference to the array to ShuffleDeck(). The C++ syntax for an array reference is data-type (&)[N] where N is the number of elements in the array. Change your function to

void ShuffleDeck( char (&rgCards)[52] ) { ... }

You can make this a template function and have the compiler deduce the array length

template<size_t N>
void ShuffleDeck( char (&rgCards)[N] ) { ... }

Finally, since you're using C++ you should probably switch over to using a container class such as std::array or std::vector instead of a C-style array.

answered Apr 5, 2012 at 21:41

Praetorian

110k20 gold badges248 silver badges340 bronze badges

Comments

Praetorian · Accepted Answer · 2012-04-06 01:15:51Z

2

You could also do this

void shuffle(int* deck, int size)
{
  for(int i =0; i < size; i++)
  {
    deck[i] = i;
  }
}

This shows that the array is indeed passed as a pointer.

int deck[52];
shuffle(deck,52);

edited Apr 6, 2012 at 1:15

Praetorian

110k20 gold badges248 silver badges340 bronze badges

answered Apr 5, 2012 at 22:29

cchampion

7,99112 gold badges45 silver badges52 bronze badges

Comments

CapelliC · Accepted Answer · 2012-04-05 21:53:02Z

1

To keep the code most similar to what you write, I'll just make minimal corrections: note that & isn't required and the index should start from 0.

void ShuffleDeck(bool rgCards[]) {
    for (int i = 0; i < 52; ++i) {
        //something
    }
}

any change you will do to rgCards[i] will be available after the call to ShuffleDeck

answered Apr 5, 2012 at 21:53

CapelliC

60.1k5 gold badges50 silver badges94 bronze badges

Comments

MSalters · Accepted Answer · 2012-04-06 07:13:46Z

0

The cleanest solution, IMO:

class Deck {
  char cards[52];
public:
  void Shuffle();
};

void Deck::Shuffle()
{
  // I can change cards here because both cards and Shuffle are members of Deck
}

answered Apr 6, 2012 at 7:13

MSalters

182k11 gold badges171 silver badges376 bronze badges

Collectives™ on Stack Overflow

How to change an array with a function?

5 Answers 5

3 Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

3 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related