Initializing a struct within a union within a struct in C

Asked Dec 09 '14 at 14:25

Active Dec 09 '14 at 16:49

Viewed 119 times

struct huffnode{
  int freq;
  union{
    struct children
    {
      struct huffnode * l;
      struct huffnode * r;
    }
    char c;
  }un;
};

I'm trying to create a program that implements a huffman tree but in order to do that I need to create nodes with a left and right node pointer in them. The problem is that I don't know how to initialize the struct children. Anyone have any ideas?

edited Dec 09 '14 at 14:37

asked Dec 09 '14 at 14:25

Rob Antcliff

3

Why you use union to store left and right child? In this way, you can only have one child at any time – D3Hunter Dec 09 '14 at 14:30
1

@jujj No, if I initialise the struct I'll be able to have the 2 children inside it. So in essence I have either the struct children or the char c in the union. – Rob Antcliff Dec 09 '14 at 14:34
@jujj Not true - look at it again. – Jonathon Reinhart Dec 09 '14 at 14:34
Pls fix your indentantion, that's painful to read – leonbloy Dec 09 '14 at 14:36
1

The `struct children` is a syntax error, it should be `struct { struct huffnode *left, *right; } children;`, now it's anonymous which is going to be confusing. – unwind Dec 09 '14 at 14:38
@unwind Anonymous member structs are allowed since C11. There's a missing semicolon though. – Lundin Dec 09 '14 at 14:39
Anyway, this code doesn't make any sense, particularly not "So in essence I have either the struct children or the char c in the union". – Lundin Dec 09 '14 at 14:41
@Lundin I know, but it's still confusing, plus I wouldn't expect C11 compilers everywhere ... Perhaps I'm being overly catious. – unwind Dec 09 '14 at 14:42
@JonathonReinhart Yes, left and right child will both inside the union as i have test it. Thanks for pointing it out – D3Hunter Dec 09 '14 at 14:45
I think I have it now. Thanks everyone. – Rob Antcliff Dec 09 '14 at 14:46
why Huffman coding structure needs `union`... it's just a simple binary tree. – Jason Hu Dec 09 '14 at 14:59

Initializing a struct within a union within a struct in C

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