Error message explained

[mdh]

I understand *why* this produces an error and how to correct it, (add
parentheses) but the error itself is a bit eclectic? As I am sure this
will arise again, could anyone throw some logic at it.

int main (int argc, const char * argv[]) {


struct point {
int x;
int y;
};

struct point *pp;
struct point origin;
pp= &origin;

origin = makepoint(23, 67);

printf("%d, %d\n", (*pp).x, *pp.y); /*error: request for member 'y'
in something not a structure or union*/

}

Thanks in advance

 

[vippstar]

I understand *why* this produces an error and how to correct it, (add
parentheses) but the error itself is a bit eclectic? As I am sure this
will arise again, could anyone throw some logic at it.

int main (int argc, const char * argv[]) {

struct point {
int x;
int y;

};

struct point *pp;
struct point origin;
pp= &origin;

origin = makepoint(23, 67);

printf("%d, %d\n", (*pp).x, *pp.y); /*error: request for member 'y'
in something not a structure or union*/

}

See operator precedence.
.. bounds tigher than *

*pp.y means *(pp.y)

pp is a pointer, . requires structure or union

 

[mdh]

I understand *why* this produces an error and how to correct it,

snip

int main (int argc, const char * argv[]) {

struct point {
   int x;
   int y;
};

   struct point *pp;
   struct point origin;
   pp= &origin;

   printf("%d, %d\n", (*pp).x, *pp.y);  /*error: request for member 'y'
in something not a structure or union*/

It's a snytax error. As written *pp.y assumes pp a structure and y a
pointer to int. None of that is true.

Thanks Joe...yes that makes sense. One more eclectism falls

 

[mdh]

pp is a pointer, . requires structure or union

thanks

 

[Harald van Dijk]

struct point *pp;
[...]
printf("%d, %d\n", (*pp).x, *pp.y); /*error: request for member 'y'
in something not a structure or union*/

It's a snytax error.

No, it's not, unless snytax is an intentional misspelling that I am not
familiar with. *pp.y is syntactically valid, but semantically invalid.

 

[gw7rib]

I understand *why* this produces an error and how to correct it, (add
parentheses) but the error itself is a bit eclectic? As I am sure this
will arise again, could anyone throw some logic at it.

int main (int argc, const char * argv[]) {

struct point {
        int x;
        int y;

};

        struct point *pp;
        struct point origin;
        pp= &origin;

        origin = makepoint(23, 67);

        printf("%d, %d\n", (*pp).x, *pp.y);  /*error: request for member 'y'
in something not a structure or union*/

}

Thanks in advance

Erm, it seems to make perfect sense to me. The '.' means you are
accessing a member of a struct or union, so pp.y means "access the
member called 'y' of the struct or union pp". Which is wrong, beacause
pp is not a struct or union - it is a pointer to a struct. So pp isn't
a struct or a union, and it doesn't have members. So it's an error to
access member 'y' of it.