list of a struct

Brandito · **Posted:** Tue 11-30-2004 2:12AM

Code:

struct chest{
  char breast;
  int tit;  //inchs in diameter
}

void main(){

  struct chest hoe;
  std::list<struct chest> beoches;

  hoe->breast = 'c';
  hoe->tit = 2;

  beoches.push_back(hoe);

  beoches.sort();
}

I have two questions...
1) for making a list of structs I do add the word struct between the < > right?
2) how do I use sort() on a struct list? I want to sort by my int value, tit in this example.

thanks,
brandito

zkissane · **Posted:** Tue 11-30-2004 12:01PM

Brandito wrote:

Code:

struct chest{
  char breast;
  int tit;  //inchs in diameter
}

void main(){

  struct chest hoe;
  std::list<struct chest> beoches;

  hoe->breast = 'c';
  hoe->tit = 2;

  beoches.push_back(hoe);

  beoches.sort();
}

I have two questions...
1) for making a list of structs I do add the word struct between the < > right?

Not in C++. Just say

Code:

std::list<chest> beoches;

In C you would have to include the struct (or do the namespace thing...), but in C you probably wouldn't be able to use the STL classes and probably wouldn't have templates. I say "probably" because I don't keep up with the latest and greatest in C.

The "namespace thing" would be something like

Code:

typedef struct CHEST {
char breast;
int tit;
} chest;

...and from then on when you wanted that object you'd just say

Code:

chest Bosom;

or something.
Don't do that in C++. At the very least it's unnecessary and at worst you'll confuse the compiler.

Quote:

2) how do I use sort() on a struct list? I want to sort by my int value, tit in this example.

This answer assumes that sort() is actually a valid method for std::list. I'll take your word that it is, but I haven't looked it up myself.

You have to provide a compare operation. It's a really weird way of doing it. IIRC, you have to do something like...

Code:

struct GreaterThan
{
   bool operator () (const Chest& a, const Chest& b)
   {
         return (a.tit > b.tit);
    }
};

Then you have to feed that struct as a template parameter somewhere, I think. Make sure that it's actually doing the comparison that the container class expects. Look on a STL website for more info; here's SGI's:
http://www.sgi.com/tech/stl/

Dr Hilgers' CS236 site has an example on how to use the comparison struct with the STL hash table.
http://web.umr.edu/~hilgers/classes/CS236/frame.html
Hit "program assignments" and pick program 7. About a third of the way down, under section "The Symbol Table" he links to some example code.

Brandito · **Posted:** Thu 12-02-2004 3:22PM

that helps a little... but I still don't know how to use the sort function like I want. I tried googling but came up short.

list of a struct

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