Thread: Function array and pointer

I can only get the first element of an array to work when passed to another function.
If i try to print out the next element of that array in that function i dont get the result i expected (the strings has 1 letter fewer from the begining when i write e.g: array+i).
Can someone please tell me what i have done wrong or what is missing?
The problem is apparent when you see the result of the printf() function, which is in the function roa() and that's where the problem lies i suspect.

Code:

/*Pointer array test.*/
#include <stdio.h>
void blank(void);
void roa(char *a,char *b,int *c);

int main(void){
int i;
int age[3] = {20,21,18};
char first[12] = "Tree";
char first1[12] = "Water";
char first2[12] = "Dirt";
char last[12] = "Strotter";
char last1[12] = "Bridge";
char last2[12] = "Stone";
char *given[3];
char *family[3];
*given = first;
*(given+1) = first1;
*(given+2) = first2;
*family = last;
*(family+1) = last1;
*(family+2) = last2;

blank();
printf("Name Lastname Age\n");
for(i=0;i<3;i++)printf("%s %s %d\n",*(given+i),*(family+i),*(age+i));    
roa(*given,*family,age);
return 0;}

void blank(void){
int i;
for(i=0;i<80;i++)printf("#");
for(i=0;i<80;i++)printf("#");
for(i=0;i<32;i++)printf(" ");printf("Array Pointer Test\n");
for(i=0;i<80;i++)printf("#");
for(i=0;i<9;i++)printf("\n");}

void roa(char *a,char *b,int *c){
int i;
printf("\nroa()\nName Lastname Age\n");
for(i=0;i<3;i++)printf("%s %s %d\n",a+i,b+i,*(c+i));}

Like so

Code:

/*Pointer array test.*/
#include <stdio.h>
void blank(void);

/* Look at the arrays you want to pass */
/* and copy the declarations.  Using meaningful names */
/* would be good as well */
void roa(char *given[], char *family[], int age[]);

int main(void)
{
  int i;
  int age[3] = { 20, 21, 18 };
  char first[12] = "Tree";
  char first1[12] = "Water";
  char first2[12] = "Dirt";
  char last[12] = "Strotter";
  char last1[12] = "Bridge";
  char last2[12] = "Stone";
  char *given[3];
  char *family[3];

  given[0] = first;
  given[1] = first1;
  given[2] = first2;
  family[0] = last;
  family[1] = last1;
  family[2] = last2;

  blank();
  printf("Name Lastname Age\n");
  for (i = 0; i < 3; i++)
    printf("%s %s %d\n", *(given + i), *(family + i), *(age + i));
  roa(given, family, age);
  return 0;
}

void blank(void)
{
  int i;
  for (i = 0; i < 80; i++)
    printf("#");
  for (i = 0; i < 80; i++)
    printf("#");
  for (i = 0; i < 32; i++)
    printf(" ");
  printf("Array Pointer Test\n");
  for (i = 0; i < 80; i++)
    printf("#");
  for (i = 0; i < 9; i++)
    printf("\n");
}

void roa(char *given[], char *family[], int age[])
{
  int i;
  printf("\nroa()\nName Lastname Age\n");
  for (i = 0; i < 3; i++)
    printf("%s %s %d\n", given[i], family[i], age[i] );
}

> *(given+1) = first1;
There is no difference between what you wrote, and what I wrote, it's all the same to the compiler.
So since it's an array, treat it like an array and use a subscript.

Oh, and learn to format code in something like a reasonable fashion.
This super-compressed eliminate as many spaces as possible doesn't help figure out what is going on, has no measureable consequence on the compiler, and absolutely no impact on the generated code.

You should use this:

Code:

void roa(char *a[3],char *b[3],int *c){
	int i;
	printf("\nroa()\nName Lastname Age\n");
	for(i=0;i<3;i++)printf("%s %s %d\n",*(a+i),*(b+i),*(c+i));
}

Or

Code:

void roa(char **a,char **b,int *c){
	int i;
	printf("\nroa()\nName Lastname Age\n");
	for(i=0;i<3;i++)
		printf("%s %s %d\n",*(a+i),*(b+i),*(c+i));
}

Second code only works for char. Else you need too specify ptr offset yourself.

> it was really hard for me to split the for loops and printf functions to seperate lines
What sort of editor are you using?
How hard can it be to press return at the point you want, and indent the code to suit?

Besides, I would prefer this

Code:

  for(i=0;i<3;i++) {
    printf("%s %s %d\n",given[i], family[i], age[i] );
  }

Always use braces even when they're apparently optional.
No end of newbies come unstuck when they forget the single-statement rule and the code does something completely different, when they try and add debug statements for example.

Example

Code:

for ( i = 0 ; i < 10 ; i++ )
  printf( "%d\n" );

for ( i = 0 ; i < 10 ; i++ )
  printf( "Inside loop\n" );  /* apparently to debug the loop... */
  printf( "%d\n" );

Which, despite it's indentation, will only be executed once when the loop exits.

pointer to array of pointer will be automaticaly pointer to pointer to pointer when passed to functions.
this is good to be read. Though it is C++.

Well, just so you know, we, too, have different tastes on how to go about things. Besides, what's so hard about going to Tools > Editor Options and checking "Auto Indent"?

Well prepare yourself for lots of frustration on your part, constant nagging from everyone else to adopt a more reasonable style, then eventually people just refusing to even look at such horrible code.

tzpb8: I would think that a structure would really lend itself to what you are doing. Something like this?

Code:

#include <stdio.h>

struct record
{
   char first[12];
   char last[12];
   int  age;
};

void record_print(struct record *rec, size_t size)
{
   printf("%-*s %-*s %s\n", (int)sizeof rec->first, "First Name", 
          (int)sizeof rec->last, "Last Name", "Age");
   for ( ; size--; ++rec )
   {
      printf("%-*s %-*s %d\n", (int)sizeof rec->first, rec->first, 
             (int)sizeof rec->last, rec->last, rec->age);
   }
}

int main(void)
{
   struct record myrecord[] =
   {
      { "Tree",  "Strotter", 20 },
      { "Water", "Bridge",   21 },
      { "Dirt",  "Stone",    18 },
   };
   record_print(myrecord, sizeof myrecord / sizeof *myrecord);
   return 0;
}

/* my output
First Name   Last Name    Age
Tree         Strotter     20
Water        Bridge       21
Dirt         Stone        18
*/

I wanted to learn pointers and arrays better but now i'm moving on to structers so thanks for the rewrite Dave but sence i cant at variables declaration inside structers assign values, how can i assign a string value to a char array like this?

Code:

char array[] = "Some text";

without defining & assigning value at declaration?


Oh and here i have a slight problem with prining out as a string.. it prints out the value good but when it is supposed to end it will printout something more, that i dont want, what is it and what can i do about it?

Code:

/* Structures */
#include <stdio.h>
void blank(void);

int main(void)
{
  int i;
  
  blank();
  
  struct wall
  {
  char array[];
  char stringPNT[];      
  } roa;

  roa.array[0] = 'B';
  roa.array[1] = 'l';
  roa.array[2] = 'u';
  roa.array[3] = 'e';
  
// though i would like to do it this way instaid...  
//  roa.array[] = "Blue";

  for(i=0;i<4;i++)
    printf("%c",roa.array[i]);
    
  *roa.stringPNT = *roa.array;  
  
  roa.stringPNT[0] = 'P';
  roa.stringPNT[1] = 'i';
  roa.stringPNT[2] = 'n';
  roa.stringPNT[3] = 'k';
  
  printf("\n");
  
  for(i=0;i<4;i++)
    printf("%c",roa.stringPNT[i]);

  printf("\n%s",roa.stringPNT);
  return 0;
}

void blank(void)
{
  int i;
  
  for(i=0;i<80;i++)
    printf("#");
  for(i=0;i<80;i++)
    printf("#");
  for(i=0;i<32;i++)
    printf(" ");
  printf("Structures\n");
  for(i=0;i<80;i++)
    printf("#");
  for(i=0;i<17;i++)
    printf("\n");
}

Originally Posted by tzpb8

I wanted to learn pointers and arrays better but now i'm moving on to structers so thanks for the rewrite Dave but sence i cant at variables declaration inside structers assign values, how can i assign a string value to a char array like this?

Code:

char array[] = "Some text";

without defining & assigning value at declaration?

I really can't parse what it is you are asking. My best guess is that you are asking for strcpy.

Woaw, it works beautifully, strcpy is exactly what i asked for, thanks again Dave your great