Databases
StackOverflow2013
Postsdbo
POReferencing a typedef as its struct counterpart
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POReferencing a typedef as its struct counterpart
    primarykey
    data
    text
    <p>Ok guys, we all know there are all lot of typedef/struct questions out there, but I feel this one is a bit of a mind bender. </p> <p>I'm simulating the neighbor interactions of a crystal lattice using strictly C. I have a struct called "ball_struct" which I typedef'ed as just "ball". The struct contains a pointer to a list of ball_structs (since I couldn't use the typedef name before its own declaration) that the ball considers its neighbors.</p> <p><strong>So here's the catch:</strong> I want to add balls to this list of list of ball_struct neighbors. When I compile (in Visual Studio 2009, no CLR support) I get: </p> <blockquote> <p>error C2440: '=' : cannot convert from 'ball *' to 'ball_struct'</p> </blockquote> <p>I'm not surprised, but I am stumped. Is there a way to cast the typedef back down to its respective struct? If not, is there anyway I can add a "ball" to a "ball_struct" list so I don't have to remove the typedef and paste "struct" keywords all over my code? Here's the code in question:</p> <p><strong>The struct / typedef:</strong></p> <pre><code>typedef struct ball_struct { double mass; vector pos, vel, acc; /* keep list of neighbors and its size */ struct ball_struct *neighbors; int numNeighbors; } ball; </code></pre> <p><strong>And the erroneous function:</strong></p> <pre><code>/* adds ball reference to the neighbor list of the target */ void addNeighbor(ball *target, ball *neighbor) { int n = target-&gt;numNeighbors; target-&gt;neighbors[n] = neighbor; // error C2440 target-&gt;numNeighbors = n+1; } </code></pre> <p>Thanks, any help is appreciated. <em>Remember, only solutions for C please.</em></p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USBradV
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COYou could write: `typedef struct ball_struct ball;` and then `struct ball_struct { ...; ball * neighbours; ... };`.
      singulars
      1. POReferencing a typedef as its struct counterpart
      1. USJonathan Leffler
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload