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int (*point_to_func)(const void*) = NULL;
void sample_func(int x, int(*save_me)(const void*)){
point_to_func = save_me;
}
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Writes binary right handed and hex left handed
typedef int (*my_func_ptr)(const void*) my_func_ptrThen you can know just by doing this:
Back to topmy_func_ptr point_to_func = NULL;
void sample_func(int x, my_func_ptr save_me)
{
point_to_func = save_me;
}
Newbie
gcc -c -W -Wall -g -I. libpriqueue/libpriqueue.c -o libpriqueue/libpriqueue.o -o simulator libpriqueue/libpriqueue.o: In function 'priqueue_init': /home/engr/reimer1/cs241/reimer1/mp4/libpriqueue/libpriqueue.c:22: multiple definition of 'compare_func' libscheduler/libscheduler.o:/home/engr/reimer1/cs241/reimer1/mp4/libscheduler/libscheduler.c:29: first defined here collect2:ld returned 1 exit status make: *** [simulator] Error 1No idea what that means because obviously it failed to compile but the compiler I guess couldn't tell me where it failed... Never had that happen before. Now I tried changing it to the way you suggested here is what I get now:
gcc -c -W -Wall -g -I. libpriqueue/libpriqueue.c -o libpriqueue/libpriqueue.o In file included from libpriqueue/libpriqueue.c:9: libpriqueue/libpriqueue.h:9: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘compare_func_ptr’ libpriqueue/libpriqueue.h:18: error: expected declaration specifiers or ‘...’ before ‘compare_func_ptr’ libpriqueue/libpriqueue.c:15: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘compare_func’ libpriqueue/libpriqueue.c:20: error: expected declaration specifiers or ‘...’ before ‘compare_func_ptr’ libpriqueue/libpriqueue.c: In function ‘priqueue_init’: libpriqueue/libpriqueue.c:23: error: ‘compare_func’ undeclared (first use in this function) libpriqueue/libpriqueue.c:23: error: (Each undeclared identifier is reported only once libpriqueue/libpriqueue.c:23: error: for each function it appears in.) libpriqueue/libpriqueue.c:23: error: ‘comparer’ undeclared (first use in this function) libpriqueue/libpriqueue.c: In function ‘priqueue_offer’: libpriqueue/libpriqueue.c:50: warning: implicit declaration of function ‘compare_func’ make: *** [libpriqueue/libpriqueue.o] Error 1And for your reference here are the .h and .c files respectively:
/*
* Machine Problem #4
* CS 241
* The University of Illinois
*/
#ifndef LIBPRIQUEUE_H_
#define LIBPRIQUEUE_H_
typedef int (*compare_func_ptr)(const void*, const void *) compare_func_ptr; //<------typedef Function pointer declaration
typedef struct priqueue_t{
struct priqueue_t * next;
void *data;
} priqueue_t;
void priqueue_init (priqueue_t *q, compare_func_ptr comparer);
int priqueue_offer (priqueue_t *q, void *ptr);
void * priqueue_peek (priqueue_t *q);
void * priqueue_poll (priqueue_t *q);
void * priqueue_at (priqueue_t *q, int index);
int priqueue_remove (priqueue_t *q, void *ptr);
void * priqueue_remove_at(priqueue_t *q, int index);
int priqueue_size (priqueue_t *q);
void priqueue_destroy (priqueue_t *q);
#endif /* LIBPQUEUE_H_ */
/*
* Machine Problem #4
* CS 241
* The University of Illinois
*/
#include <stdlib.h>
#include <stdio.h>
#include "libpriqueue.h"
/*
* You can find the struct priqueue_t in libpriqueue.h.
*/
compare_func_ptr compare_func = NULL; //<-------------Function pointer initialization
/*
* priqueue_init()
* Initializes the priqueue_t data structure.
*/
void priqueue_init(priqueue_t *q, compare_func_ptr comparer)
{
q = (priqueue_t*)malloc(sizeof(priqueue_t));
compare_func = comparer; //<----------------Function pointer assignment
q->next = NULL;
q->data = NULL;
}
/*
* priqueue_offer()
* Inserts the specified element into this priority queue.
*
* Returns: The zero-based index where ptr is stored in the priority queue,
* where 0 indicates that ptr was stored at the front of the priority queue.
*/
int priqueue_offer(priqueue_t *q, void *ptr)
{
priqueue_t * current = q;
priqueue_t * new_node = (priqueue_t *)malloc(sizeof(priqueue_t));
priqueue_t * temp = current->next;
new_node->data = ptr;
int compare_result;
int counter = 0;
if(temp == NULL){
current->next = new_node;
return counter;
}
counter++;
while(temp != NULL){
compare_result = compare_func(temp->data, new_node->data);
if(compare_result < 0){
new_node->next = temp;
current->next = new_node;
return counter;
}
else if(compare_result >= 0){
counter++;
current = current->next;
temp = temp->next;
}
}
//If we get to this point the job must be added to the end of the queue
temp->next = new_node;
new_node->next = NULL;
return counter;
}
/*
* priqueue_peek()
* Retrieves, but does not remove, the head of this queue, returning NULL if
* this queue is empty.
*
* Returns: The head of the queue, or NULL if the queue is empty.
*/
void *priqueue_peek(priqueue_t *q)
{
return q->next;
}
/*
* priqueue_poll()
* Retrieves and removes the head of this queue, or NULL if this queue
* is empty.
*
* Returns: The head of this queue, or NULL if this queue is empty.
*/
void *priqueue_poll(priqueue_t *q)
{
priqueue_t * temp = q->next;
q->next = temp->next;
return temp;
}
/*
* priqueue_at()
* Returns the element at the specified position in this list, or NULL if
* the queue does not contain an index'th element.
*
* Returns: The index'th element in the queue, or NULL if the queue does
* not contain in index'th element.
*/
void *priqueue_at(priqueue_t *q, int index)
{
priqueue_t * temp = q->next;
int i;
for(i = index; i > 0; i--){
temp = temp->next;
}
return temp;
}
/*
* priqueue_remove()
* Removes all instances of ptr from the queue. This function should not
* use the comparer function, but check if the data contained in each
* element of the queue is equal (==) to ptr.
*
* Returns: The number of entries removed.
*/
int priqueue_remove(priqueue_t *q, void *ptr)
{
int counter;
priqueue_t * temp = q->next;
priqueue_t * lead_temp = q;
while(temp != NULL){
if(temp->data == ptr){
lead_temp->next = temp->next;
free(temp);
temp = lead_temp->next;
counter++;
}
temp = temp->next;
lead_temp = lead_temp->next;
}
return counter;
}
/*
* priqueue_remove_at()
* Removes the specified index from the queue, moving later elements up
* a spot in the queue to fill the gap.
*
* Returns: The element removed from the queue, or NULL if the specified
* index does not exist.
*/
void *priqueue_remove_at(priqueue_t *q, int index)
{
priqueue_t * temp = q->next;
priqueue_t * lead_temp;
while(temp != NULL && index > 0){
temp = temp->next;
lead_temp = lead_temp->next;
index--;
}
if(temp != NULL){
lead_temp->next = temp->next;
}
return temp;
}
/*
* priqueue_size()
* Returns the number of elements in the queue.
*
* Returns: The number of elements in the queue.
*/
int priqueue_size(priqueue_t *q)
{
int counter = 0;
priqueue_t * temp = q->next;
while(temp != NULL){
temp = temp->next;
counter++;
}
return counter;
}
/*
* priqueue_destroy()
* Destroys and frees all the memory associated with q.
*/
void priqueue_destroy(priqueue_t *q)
{
priqueue_t * temp = q->next;
while(temp != NULL){
free(q);
q = temp;
temp = temp->next;
}
free(q);
}
This assignment was due 24 hours ago so I am probably not going to get any credit for it, because of these stupid compile errors (not even sure if the code works). But now I just want to get it done because it is bugging me.
Writes binary right handed and hex left handed
typedef int (*compare_func_ptr)(const void*, const void *) compare_func_ptr;This is wrong. I know I did it, it was a code snippet and I accidentally added that last my_func_ptr. Don't put that at the end, as I believe that declares a new one of that type. Just omit it.
typedef int (*compare_func_ptr)(const void*, const void *);
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