Styjun

I have to "delete" some elements from struct. For example let it be years.
So i should find them in my struct, shift them and display new struct without them.

Our professor said, that we should use pointers to structs. And i don't get it. I mean from my point of view structs works as arrays but with some specifications.

for(i = 0; i < n; ++i) 
 if ( yr == (mvbs+i) -> releaseYear) 
 for (i = pos; i < n - 1; i++)
 (mvbs+i ) -> udk = (mvbs+i+1) -> udk; //int
 (mvbs+i) -> name = (mvbs+i+1) -> name; //char
 (mvbs+i) -> genre = (mvbs+i+1) -> genre;//char
 (mvbs+i) -> creator = (mvbs+i+1) -> creator;//char
 (mvbs+i) -> releaseYear = (mvbs+i+1) -> releaseYear;//int
 (dtbs+i) -> day = (dtbs+i+1) -> day;//int
 (dtbs+i) -> month = (dtbs+i+1) -> month;//int
 (dtbs+i) -> year = (dtbs+i+1) -> year;//int
 

I guess it should shift data to "deleted" space but I get invalid array assignment with all char stuff.

Here are my structs

struct date 
 int day; 
 int month; 
 int year; 
; 

date datebase[100], *dtbs=datebase; 

struct movies 
 int udk; 
 char name[10]; 
 char genre[10]; 
 char creator[10];
 int releaseYear; 
 struct date movieRental; 
; 

movies mooviebase[100], *mvbs=mooviebase;

Invalid array assignment while shifting struct element

Warning if I indent correctly your code it is :

for(i = 0; i < n; ++i)

 if ( yr == (mvbs+i) -> releaseYear)
 
 for (i = pos; i < n - 1; i++)
 (mvbs+i ) -> udk = (mvbs+i+1) -> udk; //int
 (mvbs+i) -> name = (mvbs+i+1) -> name; //char
 (mvbs+i) -> genre = (mvbs+i+1) -> genre;//char
 (mvbs+i) -> creator = (mvbs+i+1) -> creator;//char
 (mvbs+i) -> releaseYear = (mvbs+i+1) -> releaseYear;//int
 (dtbs+i) -> day = (dtbs+i+1) -> day;//int
 (dtbs+i) -> month = (dtbs+i+1) -> month;//int
 (dtbs+i) -> year = (dtbs+i+1) -> year;//int
 

but this is not what you want because only udk is moved in the loop and for all the other element k value n-1 (I suppose pos <= n - 1) so you do for instance (mvbs+n-1) -> name = (mvbs+n) -> name, and n being visible the size you go out of the initialized part of the array or may be out of the array.

Of course you missed to add to do :

for(i = 0; i < n; ++i)

 if ( yr == (mvbs+i) -> releaseYear)
 
 for (i = pos; i < n - 1; i++) 
 (mvbs+i ) -> udk = (mvbs+i+1) -> udk; //int
 (mvbs+i) -> name = (mvbs+i+1) -> name; //char
 (mvbs+i) -> genre = (mvbs+i+1) -> genre;//char
 (mvbs+i) -> creator = (mvbs+i+1) -> creator;//char
 (mvbs+i) -> releaseYear = (mvbs+i+1) -> releaseYear;//int
 (dtbs+i) -> day = (dtbs+i+1) -> day;//int
 (dtbs+i) -> month = (dtbs+i+1) -> month;//int
 (dtbs+i) -> year = (dtbs+i+1) -> year;//int
 
 

However first what pos is ? and because you reuse/modify the variable i in the embedded for you cannot manage the case where several entries have the same releaseYear

Probably the first for is supposed to be on pos rather than on i to be more consistent and to remove the entries pos having the search year.

After the embedded for there is one less element so you need to decrease n

Note if there are several consecutive entries having the search year you can optimize to bypass them at the same time rather than to do one by one.

The type of the elements are compatible to a direct copy so the code can be simplified to be :

pos = 0;

while(pos < n)

 if ( yr == (mvbs+pos) -> releaseYear)
 
 for (i = pos; i < n - 1; i++) 
 *(mvbs+i ) = *(mvbs+i+1)
 
 n -= 1;
 
 else
 pos += 1;

and finally you can use a memmove rather than to do the copy by yourself element by element :

pos = 0;

while(pos < n)

 if ( yr == (mvbs+pos)->releaseYear)
 
 if (pos == --n)
 /* it was the last entry */
 break;
 memmove(mvbs+pos, mvbs+pos+1, (n-pos)*sizeof(movies));
 
 else
 pos += 1;

Our professor said, that we should use pointers to structs

You already use a pointer because you do not do mooviebase[pos] for instance but use mvbs+offset, but that pointer never change and you need the additional offset, so your pointer is not useful, you can do for instance :

movies * ptr = mooviebase;
movies * sup = mooviebase + n;

while (ptr != sup)

 if (yr == ptr->releaseYear)
 
 if (ptr == --sup)
 /* it was the last entry */
 break;
 memmove(ptr, ptr+1, (sup - ptr)*sizeof(movies));
 
 else
 ptr += 1;