将结构传递给函数的问题

Question

I have several years of experience with java, but I'm very new to C. I'm still struggling to figure out when and when not to use pointers. I was given this base code and need to finish the 'push' method so that it pushes the next element onto the stack, but I'm getting errors saying:

request for member 'top' in something not a structure.

#include <assert.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>

int exit_status = EXIT_SUCCESS;
#define EMPTY (-1)
#define SIZE 16

typedef struct stack stack;
   struct stack {
   int top;
   double numbers[SIZE];
};

void push (stack *the_stack, double number) {
    if(&&the_stack.top>=SIZE-1){
       printf("error");
    }else{
       the_stack.numbers[&&the_stack.top++ ] = number;
    }
}
int main (int argc, char **argv) {
  if (argc != 1) {
     fprintf (stderr, "Usage: %s\n", basename (argv[0]));
     fflush (NULL);
     exit (EXIT_FAILURE);
  }
stack the_stack;
the_stack.top = EMPTY;
char buffer[1024];
for (;;) {
   int scanrc = scanf ("%1023s", buffer);
   if (scanrc == EOF) break;
   assert (scanrc == 1);
   if (buffer[0] == '#') {
     scanrc = scanf ("%1023[^\n]", buffer);
     continue;
  }
  char *endptr;
  double number = strtod (buffer, &endptr);
  if (*endptr == '\0') {
     push (&the_stack, number);
  }else if (buffer[1] != '\0') {
     bad_operator (buffer);
  }else {
     do_operator (&the_stack, buffer);
  }
}
 return exit_status;
}

Am I overlooking something very basic?

Answer 1

When accessing members of a structure, there are two operators: The dot operator . which is used for non-pointer structures, and the "arrow" operator -> which is used for pointers to structures.

You have a pointer to a structure in your push function, so you need to use the "arrow" operator.

---

There are other problems with your code, like the double ampersand in the push function. You also don't need to flush any files when exiting the program, the runtime will do that for you.

Answer 2

It seems very clearly that you have less experience in C. There are lots of compile time errors in your code like for example : 

In push function top and numbers should be invoked as : the_stack->top the_stack->numbers[]
An arrow is used to invoke the members of a pointer variable.

Now Comparing it with Java: Java uses only references not pointers. But internally they are pointing to some location in memory.

https://www.dropbox.com/s/qfk86yb3drdlmz2/C%20to%20Java.JPG Image http://erikdemaine.org/papers/CPE98/paper.pdf Paper

Check this link to correlate C code and Java code.