Priority queues

In a priority queue a number of values are stored, each with a priority. You can quickly find the values with minimum and maximum priority. Using this data structure you can handle certain things in the order of priority. The following functions exist:

ds_priority_create()   Creates a new priority queue. The function returns an integer as an id that must be used in all other functions to access the particular priority queue. ds_priority_destroy(id)   Destroys the priority queue with the given id, freeing the memory used. Don't forget to call this function when you are ready with the structure. ds_priority_clear(id)   Clears the priority queue with the given id, removing all data from it but not destroying it. ds_priority_copy(id,source)   Copies the priority queue source into the priority queue with the given id. ds_priority_size(id)   Returns the number of values stored in the priority queue. ds_priority_empty(id)   Returns whether the priority queue is empty. This is the same as testing whether the size is 0. ds_priority_add(id,val,prio)   Adds the value with the given priority to the priority queue. ds_priority_change_priority(id,val,prio)   Changes the priority of the given value in the priority queue. ds_priority_find_priority(id,val)   Returns the priority of the given value in the priority queue. ds_priority_delete_value(id,val)   Deletes the given value (with its priority) from the priority queue. ds_priority_delete_min(id)   Returns the value with the smallest priority and deletes it from the priority queue. ds_priority_find_min(id)   Returns the value with the smallest priority but does not delete it from the priority queue. ds_priority_delete_max(id)   Returns the value with the largest priority and deletes it from the priority queue. ds_priority_find_max(id)   Returns the value with the largest priority but does not delete it from the priority queue. ds_priority_write(id)   Turns the data structure into a string and returns this string. The string can then be used to e.g. save it to a file. This provides an easy mechanism for saving data structures. ds_priority_read(id,str)   Reads the data structure from the given string (as created by the previous call).