A few questions for you experienced folks...

As most newbies (I suppose), I'm having quite some trouble with
pointers...

#include <stdio.h>

struct datatest {
int digit;
char name[50];

int main(void)
{
datatest test1, test2, *ptr;
test1.digit=10, test1.name="Test object 1", test2.digit=10,
test2.name="Test object 2";
ptr=&test1;

printf("The content of the current digit is %d and the content of the
current name is %c",*ptr.digit, *ptr.name);
ptr++;
printf("The content of the current digit is %d and the content of the
current name is %c",*ptr.digit, *ptr.name);

Error message: Structure required on left side of . or .*

What's wrong with this code? I've understood the basic fundamentals of
"int pointers", but what about structs? Does it have anything to do
with the priorities of * and . ? Please enlighten me (and, as I think
I've pretty adequately understood the basic fundamentals of C, tell me
what to move on to...)...

...

I also want some opinions about how to correct
"clumsy code"... For example, this

{
.......

double pvnrt(double p, double V, double n, double T)
{
if (V==0) return (n*Rgas*T)/p;
if (p==0) return (n*Rgas*T)/V;
if (n==0) return (p*V)/(Rgas*T);
if (T==0) return (p*V)/(Rgas*n);
return -1;

is a simple math/chemistry function... How can this be minimized?
Also, if "x" is input, how do you process this?

The function above works when you feed it with pvnrt(1,1,1,0), then
returning T... how do you modify it so you can feed it with the char
'x' and return the unknown value (or return -1 if more than one 'x' is
input)?

Also, is this optimized?

int dice(int n, int s)
{
int a=1, returnvalue=rand()%s;
while (a++<=n) returnvalue+=rand()%s;
return returnvalue;

Notably, I want to keep my code as small as possible... Not just for
optimization cases, but I also like the look of "clean code"...

Thanks in advance...

--Joakim Persson
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Libertarian, Power Metal Fanatic,      
Guitarist, Computer/Internet {*filter*}             IRC: Efnet, Quakenet
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

   A few questions for you experienced folks...

   As most newbies (I suppose), I'm having quite some trouble with
   pointers...

Your code and your error message reveal that in fact you're writing
C++ code.  As such, it would probably be more appropriate to post to a
C++ newsgroup.
--
(supporter of the campaign for grumpiness where grumpiness is due in c.l.c)

Please: do not email me copies of your posts to comp.lang.c
        do not ask me C questions via email; post them instead

when using a pointer-to-a-structure, you can't use . to access
the members.  you must use "->".

---
John Gordon                  "No Silicon Heaven?  Preposterous!  Where would

And, as I just found out, you can put the pointer in paranthesis... so
my previous "*ptr.digit" should have been "(*ptr).digit". It works
fine now. If anyone has any other comments, please respond about the
"optimization" issues...

BTW, I haven't understood the -> method... Please provide me with an
example!

another pointer is required here
ie datatest test1, test2, *ptest1, *ptest2;

then initialise pointers with
ptest1 = &test1;
ptest2 = &test2;
ptr++ is now defunct, which was probably giving spurious results anyway
and your printf statements will become
printf("The content of the current digit is %d and the content of the
current name is %c",*ptestn.digit, *ptestn.name);

just replace . with ->

instead of "struct.member" use "struct->member"

---
John Gordon                  "No Silicon Heaven?  Preposterous!  Where would

   And, as I just found out, you can put the pointer in paranthesis... so
   my previous "*ptr.digit" should have been "(*ptr).digit". It works
   fine now. If anyone has any other comments, please respond about the
   "optimization" issues...

   BTW, I haven't understood the -> method... Please provide me with an
   example!

(*a).b is equivalent to a->b.
--
(supporter of the campaign for grumpiness where grumpiness is due in c.l.c)

Please: do not email me copies of your posts to comp.lang.c
        do not ask me C questions via email; post them instead

You want to define a structur type.

typedef struct s {
   int digit;
   char name[50];

Now in main() test1 and test2 become structures and ptr a pointer
to structure.

After assignment "ptr = &test1;" you must dereference the pointer to get
the structure.  "(*ptr).name" for example.  C provides a short-hand for
this construct as "ptr->name".  They are otherwise equivalent.

--

"Everything should be made as simple as possible, but not simpler."
                    --- Albert Einstein ---

Instead of (*ptr).digit write ptr->digit.

The advantage may not be clear in this particular case, but imagine what
happens if you have a pointer to a structure, a member of which is a pointer
to another structure, a member of which is 'digit'.  With the
stars-and-parentheses form you'd have to write

  (*(*ptr1).ptr2).digit

which is getting messy, while with -> you can just do

  ptr1->ptr2->digit

Cheers,
Richard
--
Richard Stamp, Bournemouth, UK

Its precedence is such that you can write expressions such as
 head->next->next without worrying about parens and stuff. Makes my code
look a lot neater!!!!

--
"I see you have books under your arm, brother. It is indeed a rare pleasure
these days to come across somebody that still reads, brother."

        - Anthony Burgess

Or by adding braces:
   (*ptr).digit

Stephan
(initiator of the campaign against grumpiness in c.l.c)