声明“struct”类型的原型 - C.

Question

I've been racking my brains on this for a while, I'm simply trying to create a method that returns a struct as I wish to return two int's.

My prototype for the method is as follows:

typedef struct RollDice();

Also the method itself:

typedef struct RollDice()
{
 diceData diceRoll;

 diceRoll.dice1 = 0;
 diceRoll.dice2 = 0;

 return diceRoll;
}

The compiler shows the error: "Syntax error: ')'" for both the prototype and actual method.

The struct itself:

typedef struct
{
 int dice1;
 int dice2;
}diceData;

Is it obvious where I'm going wrong? I've tried everything I can think of.

Thanks

Edit/Solution:

To get the program to work with the suggested solutions I had to make the following changes to the struct,

typedef struct diceData
    {
     int dice1;
     int dice2;
    };

Answer 1

You'll want typedef struct ... diceData to occur before your function, and then the signature of the function will be diceData RollDice() .

typedef <ORIGTYPE> <NEWALIAS> means that whenever <NEWALIAS> occurs, treat it as though it means <ORIGTYPE> . So in the case of what you've written, you are telling the compiler that struct RollDice is the original type (and of course, there is no such struct defined); and then it sees () where it was expecting a new alias.

Answer 2

This is just a concrete version of Mark Rushakoff's answer:

typedef struct
{
  int dice1;
  int dice2;
} diceData;

diceData RollDice()
{
  diceData diceRoll;

  diceRoll.dice1 = 0;
  diceRoll.dice2 = 0;

  return diceRoll;
}

Answer 3

You can't use typedef to define a function.

Typedef your struct first like

typedef struct
{
    int dice1;
    int dice2;
} diceData;

Then declare your function as

diceData RollDice()
{
    diceData diceRoll;

    diceRoll.dice1 = 0;
    diceRoll.dice2 = 0;

    return diceRoll;
}

That declares RollDice as a function that returns a diceData struct.

An alternative way to deal with trying to return two values would be to use out parameters.

In that case your function would return a boolean (to indicate success or failure) and take two pointers to integers as parameters. Within the function you'd populate the contents of the pointers, like this:

bool_t rollDice(int *pDice1, int *pDice2)
{
    if (pDice1 && pDice2)
    {
        *pDice1 = 0;
        *pDice2 = 0;
        return TRUE;
    }
    else
    {
        return FALSE;
    }
}

int main(int argc, char **argv)
{
    int a, b;
    rollDice(&a, &b);

    return 0;
}

Answer 4

The problem is you haven't given the method a return type. It looks like you should be returning a dicedata type so the prototype signature would look like

struct dicedata RollDice();

And the method

struct dicedata RollDice()
{
    diceData diceRoll;

    diceRoll.dice1 = 0;
    diceRoll.dice2 = 0;

    return diceRoll;
}