(Trivial) pointer question

**serge** · 03-30-2011

Hello

I have very little programming experience with C++. I have something like this:

Code:

bool MYFUNC( const unsigned *N, double *prob, double *corr )
{
bool flag = false;
printf( "%u ; %f ; %f\n" , *N , *prob , *corr );

double ma[ *N ] = {0.0}; // ERROR

// other things

return( flag );
}

int main()
{
const unsigned n = 9;
static double p = 0.5;
static double c = 0.1;

MYFUNC ( &n , &p , &c );
}

I want to pass three pointers to MYFUNC and in it initialize a array of size N called "ma". This produces an error. Why? Actially I want to initialize an array of size (N+1).

Thanks for you help
Serge

**anon** · 03-30-2011

When you declare an automatic array in C++, the size of it must be a compile-time constant (OTOH, in C99 variable-length arrays are legal).

So you'd either use a fixed-size array which you hope is large enough, or allocate it dynamically (use std::vector).

**Elysia** · 03-30-2011

I urge you not to use printf. Use std::cout and I/O manipulators. You can also use Boost.Format (although that documentation is ........ty, to say the least).
Also prefer to pass by reference instead of by address.

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