searching a linked list for several atributes

[kotoko]

I need to provide functionality in a program that needs to search through a linked list of dinners.

The problem is I need to be able to search for every single attribute. So for the code

Restaurante* encontrarRestauranteString (char* string){
	No* auxiliar = cabeca;
	No* anterior = NULL;
	int encontrou = F;
	
	for(; auxiliar != NULL && encontrou == F; auxiliar=auxiliar->proximo)
		{
			if(auxiliar->restaurante->localizacao.latitude == coord->latitude )
			{
				return auxiliar->restaurante;
			}
			else
				anterior=auxiliar;
		}
		return NULL;
}

All I need to do is change the attribute of restaurante for every single attribute. Do I need to do this manually or can I somehow tell it in the incoming variables which thing I'm interested in so it would look something like

Restaurante* encontrarRestauranteString (?? attribute, char* value_of_attribute){
	No* auxiliar = cabeca;
	No* anterior = NULL;
	int encontrou = F;
	
	for(; auxiliar != NULL && encontrou == F; auxiliar=auxiliar->proximo)
		{
			if(auxiliar->restaurante->atribute ==  value_of_attribute)
			{
				return auxiliar->restaurante;
			}
			else
				anterior=auxiliar;
		}
		
		return NULL;
}

Don't know if I was able to explain my question properly. Please tell me if I didn't.
Thanks in advance.

[matsp]

You could probably write a function that "compare an item with a template item", where the template item has a "special value" for items that are "don't care".

For example:

struct item
{
    int lat, lon;
    char descr;
    double price;
};


// Return 0 for match, non-zero for non-match
// tempItem is a template to match. 
// In tempItem, a value of -1 for integer and float values means "don't care"
// whilst a NULL for strings means don't care. 
int match_items(const struct item *anItem, const struct item *tempItem)
{
    if (tempItem->lat != -1 && tempItem->lat != anItem->lat)
       return 1;
    if (tempItem->lon != -1 && tempItem->lon != anItem->lon)
       return 1;
    if (tempItem->descr != NULL && strcmp(tempItem->descr, anItem->descr))
       return 1;
    if (tempItem->price != -1.0 && fabs(tempItem->price - anItem->price) > 0.01)
       return 1;
    // If all match, return 0 to indicate a match.
    return 0;
}

Note that we avoid direct comparison of floating point except for the -1.0 constant, since direct comparisons of float is possibly not matching for certain values, if one is produced through calculation and another isn't.

[You may also want to have a "delta" in other comparisons, so that for example a latitude/longitude comparison allows a certain small difference between the target and the actual value]

There are possibly ways that you could use offsetof() and macros to do something else, but it's a lot more advanced, and would not be particularly easy to explain or write. And you still essentially need to know what each field is in the structure, so I don't think it's a better solution.

--
Mats

[kotoko]

I thought that I needed some kind of feature of C that I didn't know about but that's pretty straight forward and much much better.

Thanks lot!