Pointer to Structure Error Message

[johndeaton]

Hello All,
I am working through the example problem at Prime Pattern | CodeChef. (As a side note: This is a very good site for anyone that wants to practice their programming skills.) I have made a structure and pointer to it. I am getting a compiler error that I don't understand. Here is my structure and pointer:

typedef struct
{
   int8_t x_coor;
   int8_t y_coor;
   uint8_t square_count;
   uint8_t move_count;
} movement;

typedef movement *pt_to_movement;

Here is where I defined one of each and tried to assign the address of the structure to the pointer.

void moving_init(void)
{
   movement mover;
   pt_to_movement pt_to_mover;
   pt_to_mover &mover;
   mover.x_coor = 0;
   mover.y_coor = 0;
   mover.square_count = 0;
   mover.move_count = 0;
}

The error says: invalid operands to binary & (have 'pt_to_movement' and 'movement'). It is pointing to the line: pt_to_mover &mover;

I'm sure I'm missing something simple. Anyone see the problem?

Thanks

[laserlight]

Don't do this:

typedef movement *pt_to_movement;

It is clear that movement* is the type "pointer to movement", so a typedef does not help. Rather:

movement mover;
movement *pt_to_mover = &mover;

[johndeaton]

Don't do this:

typedef movement *pt_to_movement;

It is clear that movement* is the type "pointer to movement", so a typedef does not help. Rather:

movement mover;
movement *pt_to_mover = &mover;

This worked. Thanks. I'm still unsure why mine didn't work though. In this case, making a typedef of the pointer was trivial. But, in a larger program it might be useful. Do you know why I got the error message that I did? Thanks.

[laserlight]

I'm still unsure why mine didn't work though.

Look at this line:

pt_to_mover &mover;

Allow me to insert a space:

pt_to_mover & mover;

What you are doing is trying to take the bitwise and operation between pt_to_mover and mover, then discard the result. However, these objects don't allow for bitwise and, thus the compile error.

In this case, making a typedef of the pointer was trivial. But, in a larger program it might be useful.

That is true. It would be useful if you were creating a typedef for an opaque pointer type.

[johndeaton]

Thanks for your comments.
John