Thread: How do I do this??

Hey guys,
I have a compare function which receives at different times either first name, last name and maybe even both? Initially when wrote my lab it was only for the first name..how do I modify the code to accomodate for both first name or last name..(first name and last name are fields in the KEY structure of a linked list)..any ideas?

strcture KEY contains an array for first names and another array for last names..

This was my initial code..how do I modify it?

Code:

int cmp(KEY k, KEY k2)
{
	int cmp = 0;
	cmp = strcmp(k.names, k2.names);
	return cmp; 
}

and this is my search function that gets first name OR last name OR both..

Code:

int searchList(NODE *pList, 
			   NODE **pCur,
			   NODE **pPre,
			   KEY k)

{
	int found = 0;
	// initialize
	*pPre = NULL;
	*pCur = pList;

	//Start search
	while(*pCur != NULL && (cmp(k, (*pCur)->directory.k) > 0))
	{
		*pPre = *pCur;
		*pCur = (*pCur)-> next;
	}

	if(*pCur && (cmp(k, (*pCur)->directory.k) == 0))
	{
		found = 1;
	}

	return found; 
}

Currently, this search function works just fine if I want to look up the directory using first names..need to modify it so that I can search using last names as well. Any ideas?

The main idea behind the code is that it should be generic. Thats what the purpose of the project is: to recycle code..
Thanks
A

Using function pointers would be one way - see the standard function qsort for the general idea

Code:

int cmp_first (KEY k, KEY k2) {
  return strcmp(k.names, k2.names);
}
int cmp_last (KEY k, KEY k2) {
//  your new code for comparing last names
}
int cmp_both (KEY k, KEY k2) {
//  your new code for comparing both names
}
int searchList ( NODE *pList, NODE **pCur, NODE **pPre,
  KEY k,  int (*cmp)(KEY,KEY) ) {
// your existing code
}

Then you would just choose which compare function you want to use, when you call searchList
searchList ( ...., cmp_first );

hi Salem,
do you wanna explain that a little bit more..please?
A

would my calling statement look like this cos it causes a lot of errors.
temp = searchList(pList, &pCur, &pPre, k2, (*cmp)(KEY,KEY));
??

Originally posted by aspand
would my calling statement look like this cos it causes a lot of errors.
temp = searchList(pList, &pCur, &pPre, k2, (*cmp)(KEY,KEY));
??

If you want search on the first name you call:

Code:

temp = searchList(pList, &pCur, &pPre, k2, cmp_first);

If you want to search on the last name you call:

Code:

temp = searchList(pList, &pCur, &pPre, k2, cmp_last);

ah..gotcha Monster..though I am still a lil fuzzy over the prototype declaration for the same..
should it be (int)(cmp*)(KEY, KEY)? aren't I just calling one function then?? or would I change it accordingly?

Originally posted by aspand
ah..gotcha Monster..though I am still a lil fuzzy over the prototype declaration for the same..
should it be (int)(cmp*)(KEY, KEY)? aren't I just calling one function then?? or would I change it accordingly?

No it's *cmp because you pass the address of the function.
I think you can also call the functions like this:

Code:

temp = searchList(pList, &pCur, &pPre, k2, &cmp_first);

But when passing a function you don't need to add the &.
You automatically get a function pointer...