"Invalid operands to binary expressions" Error - c

Question

I keep getting this error:
"Invalid operands to binary expressions ('int' and 'Primenumber'(aka
'struct number'))
on two lines that i've marked below with **'s. Whats wrong and how can I fix it? The code is for a data structure assignment.
typedef struct number
{
int num[3];
} Primenumber;
typedef struct node
{
int data;
struct node *next;
} Node;
Node *head = NULL;
int AddPrimeNumber(Primenumber x)
{
Node *n;
Node *newNode;
//Create a new node
newNode = (Node*)malloc(sizeof(Node));
**newNode->data=x;**
newNode->next=NULL;
if (head == NULL)
{
head = newNode;
}
else
{
n= head;
while (n-> next != NULL)
{
n= n->next;
}
n->next= newNode;
}
return 0;
}
int SearchPrimeNumber(Primenumber x)
{
int pos=0;
Node *n = head;
while (n != NULL)
{
**if (n->data ==x)**
{
return pos;
}
else
{
pos++;
n= n->next;
}
}
return 0;
}
int DisplayPrimeNumber()
{
Node *n =head;
while (n != NULL)
{
printf("%d -> ", n->data);
n= n->next;
}
printf("\n");
return 0;
}

Answer 1

First time
newNode->data=x;
you are assigning an struct of PrimeNumber type to an int,
Second time you are comparing an struct of PrimeNumber type to an int
n->data ==x
both are wrong, may be what you want is
typedef struct Node {
PrimeNumber data;
struct Node *next;
};
the assignment part will be ok, but you will have to elaborate on the comparison part I would use a function
areEqualPrimeNumbers(PrimeNumber *x, PrimeNumber *y)
{
return ((x->num[0] == y->num[0]) && (x->num[1] == y->num[1]) && (x->num[2] == y->num[2]));
}
or if you want to use memcmp
areEqualPrimeNumbers(PrimeNumber *x, PrimeNumber *y)
{
return (memcmp(x->num, y->num, sizeof(x->num)) == 0);
}
and then
areEqualNodes(&x, &(n->data));
the memcmp version is better since it does not depend on the definition of PrimeNumber.

Answer 2

newNode->data is of type int while x is of type Primenumber (struct number). C provides no operation on entire structure except assignment.

Answer 3

In first **s you are trying to assign x of type Primenumber to n->data of type int;This is your first mistake.
In second **s you are trying the same for comparing;This is your second mistake.
And,please mark your errors with simple //error comments,not using **s ;).

Answer 4

// always comment your code so others (or yourself later)
// do not have to 'reverse engineer' it
// <-- declutter code by just defining a struct type, not typedef struct
struct PrimeNumber
{
int num[3];
};
struct Node
{
int data;
struct node *next;
};
// <-- due to better definition of struct, need to use the 'struct' modifier
struct Node *head = NULL;
// <-- pass as pointer so compiler does not generate two hidden calls to memcpy())
// <-- nor allocate memory space that is unusable for anything else
//int AddPrimeNumber(PrimeNumber x)
// <-- due to better definition of struct, need to use the 'struct' modifier
int AddPrimeNumber(struct PrimeNumber* x)
{
// <-- due to better definition of struct, need to use the 'struct' modifier
// <-- initialize local variables to a 'safe' value
struct Node *n = NULL;
struct Node *newNode = NULL;
//Create a new node
// <-- always check the returned value from malloc() to assure operation successful
if( NULL == (newNode = malloc(sizeof(Node)) ) )
{ // then malloc failed
perror( "malloc failed" );
exit( EXIT_FAILURE );
}
// implied else, malloc successful
// <-- x contains 3 integer fields, newNode contains 1 integer field.
// <-- what were you expecting to happen?
// <-- perhaps you meant: newNode->data = x->num[0]; which only copies one int, not all three
**newNode->data=x;**
newNode->next=NULL;
if (head == NULL) // this handles special case of empty list
{
head = newNode;
}
else
{ // else, list already contains one or more nodes
n= head;
while (n->next != NULL)
{
// step to next node in linked list
n= n->next;
}
// <-- currently 'n' points to last node in linked list
// <-- add new node to end of linked list
n->next= newNode;
}
return 0;
} // end function: AddPrimeNumber
// similar considerations need to be applied to the other posted function