Why doesn't this code compile? - object assignment, call, increment, decrement and new can be used as instruction

Question

I'm testing some code in C# from Visual Studio Express 2008:

delegate void Hm(int k);

static void Main(string[] args)
{
    char[] m = new char[10];

    m[0] = 'H'; m[5] = 'M';
    m[1] = 'o'; m[6] = 'u';
    m[2] = 'l'; m[7] = 'n';
    m[3] = 'a'; m[8] = 'd';
    m[4] = ' '; m[9] = 'o';

    unsafe { fixed (char* p = m) { Hm H = (k) => recurd(k, p); H(0); } }
    Console.ReadLine();
}

static unsafe int recurd(int i, char* p) 
{
      Console.WriteLine(p[i]); 
      if (i == 10) return 0; else return recurd(i + 1, p);    
}

It compiles perfectly, but if I make a little change in the "recurd" function:

static unsafe int recurd(int i, char* p) 
{
      Console.WriteLine(p[i]);
      i == 10 ? 0 : recurd(i + 1, p);
     // if (i == 10) return 0; else return recurd(i + 1, p);    
}

I got an error that says "Just the expressions of object assignment, call, increment, decrement and new can be used as instruction" (It's a translation from spanish).

Why do I get this error? How can I fix it?

Answer 1

You're missing the "return" keyword:

return i == 10 ? 0 : recurd(i + 1, p);

Answer 2

i = (i == 10) ? 0 : recurd(i + 1, p);

Answer 3

Try this:

static unsafe int recurd(int i, char* p) 
{
      Console.WriteLine(p[i]);
      return i == 10 ? 0 : recurd(i + 1, p);
}

It's complaining because you're not doing anything with the result of the expression.

Answer 4

This one

static unsafe int recurd(int i, char* p) 
{
      Console.WriteLine(p[i]);
      i == 10 ? 0 : recurd(i + 1, p);
     // if (i == 10) return 0; else return recurd(i + 1, p);    
}

won't work because it doesn't return anything.

Answer 5

Should be: return i == 10 ? 0 : recurd(i + 1, p);

You forgot to add your return in.

Answer 6

I tried: i= i == 10 ? return 0 : return recurd(i + 1, p);

and also i == 10 ? return 0 : return recurd(i + 1, p);

And I get errors.

But I tried: return i== 10 ? 0 : recurd(i + 1, p);

And It works!! Thanks Joel! Thanks Jonathan!

My mistake was thinking that the value was automatic returned and the word "return" was no necesary.

Answer 7

I tried: i= i == 10 ? return 0 : return recurd(i + 1, p);

and also i == 10 ? return 0 : return recurd(i + 1, p);

And I get errors.

But I tried: return i== 10 ? 0 : recurd(i + 1, p);

And It works!! Thanks Joel! Thanks Jonathan!

My mistake was thinking that the value was automatic returned and the word "return" was no necesary.