pre increment struct single pointer

In this section, you are going to learn

How to iterate structure array using ++ptr ?

What is the meaning of ++ptr, *++ptr, *(++ptr), *++(ptr), ++(*ptr), ++*ptr ?

What is the meaning of c = ++ptr, c = *++ptr, c = *(++ptr), c = *++(ptr), c = ++(*ptr), c = ++*ptr ?

What is the difference between ++ptr, *++ptr, *(++ptr), *++(ptr), ++(*ptr), ++*ptr ?

What is the difference between c = ++ptr, c = *++ptr, c = *(++ptr), c = *++(ptr), c = ++(*ptr), c = ++*ptr ?

Topics of Pre Increment

• Basics of Pre Increment

• Meaning of expressions

• Summary of expressions

• Pre Increment : struct pointer inside structure

• Pre Increment : Function Call

Basics of Pre Increment

• ++ptr Basic Usage

• ++ptr : Iterate and print structures of an structure array

Example 1 : ++ptr : Basic Usage

• Step 1 : Define a Single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Point ptr to Single dimension array

struct User_Data *ptr;

ptr = arr;

• Step 3 : Increment ptr

++ptr;

• Step 4 : Print *ptr

printf("ptr->a = %d\n", ptr->a);
printf("ptr->b = %d\n", ptr->b);

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct User_Data *ptr;

        ptr = arr;

        ++ptr;

        printf("ptr->a = %d\n", ptr->a);
        printf("ptr->b = %d\n", ptr->b);

        return 0;
}

• Output is as below

ptr->a = 2
ptr->b = 3

Example 2 : ++ptr : Iterate and print structures of an structure array

• Step 1 : Define a Single Dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Point ptr to Single dimension array

struct User_Data *ptr;

ptr = arr;

• Step 3 : Print structure array by iterating through all structures using ++ptr

for (int i = 0; i < 3; i++)
{
        printf("ptr->a = %d\n", ptr->a);
        printf("ptr->b = %d\n", ptr->b);
        ++ptr;
}

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct User_Data *ptr;

        ptr = arr;

        for (int i = 0; i < 3; i++)
        {
                printf("ptr->a = %d\n", ptr->a);
                printf("ptr->b = %d\n", ptr->b);
                ++ptr;
        }

        return 0;
}

• Output is as below

ptr->a = 0
ptr->b = 1
ptr->a = 2
ptr->b = 3
ptr->a = 4
ptr->b = 5

Meaning of expressions

• Meaning of ++ptr and c = ++ptr

• Meaning of *(++ptr) and c = *(++ptr)

• Meaning of *++ptr and c = *++ptr

• Meaning of *++(ptr) and c = *++(ptr)

• Meaning of ++(*ptr) and c = ++(*ptr)

Meaning of ++ptr and c = ++ptr

• Consider statement

p = ++ptr;

• There are two steps in this statement

  • ptr is incremented

  • Current value of ptr is assigned to p

• We now derived a rule

  • First Increment, then Assign

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Define a single pointer and point to array

struct User_Data *ptr;

ptr = arr;

OR

struct User_Data *ptr;

ptr = &arr[0];

• Step 3 : Iterate and print the structure array

for (int i = 0; i < 2; i++)
{
        struct User_Data *p;

        p = ++ptr;

        printf("p->a = %d\n", p->a);
        printf("p->b = %d\n", p->b);
}

Can you guess what is happening ?

• Let us Recall

p = ++ptr;

• There are two steps in this statement

  • ptr is incremented

  • Current value of ptr is assigned to p

• We now derived a rule

  • First Increment, then Assign

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct User_Data *ptr;

        ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data *p;

                p = ++ptr;

                printf("p->a = %d\n", p->a);
                printf("p->b = %d\n", p->b);
        }

        return 0;
}

• Output is as below

ptr->a = 2
ptr->b = 3
ptr->a = 4
ptr->b = 5

Meaning of *(++ptr) and c = *(++ptr)

• Consider statement

c = *(++ptr);

• There are two steps in this statement

  • ptr is incremented

  • Current value of *ptr is assigned to c

  • *ptr is NOT incremented

• We now derived a rule

  • First Increment, then Assign

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Define a single pointer and point to array

struct User_Data *ptr;

ptr = arr;

OR

struct User_Data *ptr;

ptr = &arr[0];

• Step 3 : Iterate and print the structure array

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *(++ptr);

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

Output is as below

Can you guess what is happening ?

• Let us Recall

c = *(++ptr);

• There are two steps in this statement

  • ptr is incremented

  • Current value of *ptr is assigned to c

  • *ptr is NOT incremented

• We now derived a rule

  • First Increment, then Assign

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct User_Data *ptr;

        ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *(++ptr);

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Meaning of *++ptr and c = *++ptr

• Same as *(++ptr) and c = *(++ptr)

• Consider statement

c = *++ptr;

• There are two steps in this statement

  • ptr is incremented

  • Current value of *ptr is assigned to c

  • *ptr is NOT incremented

• We now derived a rule

  • First Increment, then Assign

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Define a single pointer and point to array

struct User_Data *ptr;

ptr = arr;

OR

struct User_Data *ptr;

ptr = &arr[0];

• Step 3 : Iterate and print the structure array

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++ptr;

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

Can you guess what is happening ?

• Let us Recall

c = *++ptr;

• There are two steps in this statement

  • ptr is incremented

  • Current value of *ptr is assigned to c

  • *ptr is NOT incremented

• We now derived a rule

  • First Increment, then Assign

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct User_Data *ptr;

        ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++ptr;

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Meaning of *++(ptr) and c = *++(ptr)

• Same as *(++ptr) and c = *(++ptr)

• Consider statement

c = *++(ptr);

• There are two steps in this statement

  • ptr is incremented

  • Current value of *ptr is assigned to c

  • *ptr is NOT incremented

• We now derived a rule

  • First Increment, then Assign

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Define a single pointer and point to array

struct User_Data *ptr;

ptr = arr;

OR

struct User_Data *ptr;

ptr = &arr[0];

• Step 3 : Iterate and print the structure array

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++(ptr);

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

Can you guess what is happening ?

• Let us Recall

c = *++(ptr);

• There are two steps in this statement

  • ptr is incremented

  • Current value of *ptr is assigned to c

  • *ptr is NOT incremented

• We now derived a rule

  • First Increment, then Assign

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct User_Data *ptr;

        ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++(ptr);

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Meaning of ++(*ptr) and c = ++(*ptr)

• Consider statement

c = ++(*ptr);

• This is invalid usage for a structure pointer !

Summary of expressions

• Summary of Pre Increment expressions

Summary of Pre Increment expressions

Expression	Explanation
c = ++ptr	Increment ptr Assign ptr to c
c = *++ptr	Increment ptr Assign *ptr to c DO NOT increment *ptr
c = *(++ptr)	Increment ptr Assign *ptr to c DO NOT increment *ptr
c = *++(ptr)	Increment ptr Assign *ptr to c DO NOT increment *ptr
c = ++*ptr	INVALID for structure pointer
c = ++*(ptr)	INVALID for structure pointer

Pre Increment : struct pointer inside structure

• Structure pointer accessed using Structure Object

• Structure pointer accessed using Structure Single Pointer

• Structure pointer accessed using Structure Double Pointer

• Structure pointer accessed using Structure Triple Pointer

• Structure pointer accessed using Nested Structure Object

• Structure pointer accessed using Nested Structure Single Pointer

• Structure pointer accessed using Nested Structure 2 level Pointers

Structure pointer accessed using Structure Object

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Create a structure object

struct ABC
{
        struct User_Data *ptr;
};

struct ABC abc;

• Step 3 : Point single structure pointer to single dimension array

abc.ptr = arr;

• Step 4 : Iterate through single dimension array using pointer

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++abc.ptr;

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

struct ABC
{
        struct User_Data *ptr;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct ABC abc;

        abc.ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++abc.ptr;

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Structure pointer accessed using Structure Single Pointer

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Allocate memory for structure pointers

struct ABC
{
        struct User_Data *ptr;
};

struct ABC *sp;

sp = malloc(sizeof(struct ABC));

• Step 3 : Point single structure pointer to single dimension array

sp->ptr = arr;

• Step 4 : Iterate through single dimension array using pointer

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++sp->ptr;

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

• Step 5 : Free memory after use

free(sp);

• See full program below

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

struct User_Data {
        int a;
        int b;
};

struct ABC
{
        struct User_Data *ptr;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct ABC *sp;

        sp = malloc(sizeof(struct ABC));

        sp->ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++sp->ptr;

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        free(sp);

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Structure pointer accessed using Structure Double Pointer

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Allocate memory for structure pointers

struct ABC
{
        struct User_Data *ptr;
};

struct ABC **dp;

dp = malloc(sizeof(struct ABC *));
*dp = malloc(sizeof(struct ABC ));

• Step 3 : Point single structure pointer to single dimension array

(*dp)->ptr = arr;

• Step 4 : Iterate through single dimension array using pointer

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++(*dp)->ptr;

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

• Step 5 : Free memory after use

free(*dp);
free(dp);

• See full program below

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

struct User_Data {
        int a;
        int b;
};

struct ABC
{
        struct User_Data *ptr;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct ABC **dp;

        dp = malloc(sizeof(struct ABC *));
        *dp = malloc(sizeof(struct ABC ));

        (*dp)->ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++(*dp)->ptr;

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        free(*dp);
        free(dp);

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Structure pointer accessed using Structure Triple Pointer

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Allocate memory for structure pointers

struct ABC
{
        struct User_Data *ptr;
};

struct ABC ***dp;

dp = malloc(sizeof(struct ABC **));
*dp = malloc(sizeof(struct ABC *));
**dp = malloc(sizeof(struct ABC ));

• Step 3 : Point single structure pointer to single dimension array

(**dp)->ptr = arr;

• Step 4 : Iterate through single dimension array using pointer

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++(**dp)->ptr;

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

• Step 5 : Free memory after use

free(**dp);
free(*dp);
free(dp);

• See full program below

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

struct User_Data {
        int a;
        int b;
};

struct ABC
{
        struct User_Data *ptr;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct ABC ***dp;

        dp = malloc(sizeof(struct ABC **));
        *dp = malloc(sizeof(struct ABC *));
        **dp = malloc(sizeof(struct ABC ));

        (**dp)->ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++(**dp)->ptr;

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        free(**dp);
        free(*dp);
        free(dp);

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Structure pointer accessed using Nested Structure Object

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Create a structure object

struct PQR
{
        struct User_Data *ptr;
};

struct ABC
{
        struct PQR pqr;
};

struct ABC abc;

• Step 3 : Point single structure pointer to single dimension array

abc.pqr.ptr = arr;

• Step 4 : Iterate through single dimension array using pointer

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++abc.pqr.ptr;

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

struct PQR
{
        struct User_Data *ptr;
};

struct ABC
{
        struct PQR pqr;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct ABC abc;

        abc.pqr.ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++abc.pqr.ptr;

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Structure pointer accessed using Nested Structure Single Pointer

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Allocate memory for structure pointers

struct PQR
{
        struct User_Data *ptr;
};

struct ABC
{
        struct PQR pqr;
};

struct ABC *sp;

sp = malloc(sizeof(struct ABC));

• Step 3 : Point single structure pointer to single dimension array

sp->pqr.ptr = arr;

• Step 4 : Iterate through single dimension array using pointer

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++sp->pqr.ptr;

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

• Step 5 : Free memory after use

free(sp);

• See full program below

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

struct User_Data {
        int a;
        int b;
};

struct PQR
{
        struct User_Data *ptr;
};

struct ABC
{
        struct PQR pqr;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct ABC *sp;

        sp = malloc(sizeof(struct ABC));

        sp->pqr.ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++sp->pqr.ptr;

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        free(sp);

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Structure pointer accessed using Nested Structure 2 level Pointers

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Allocate memory for structure pointers

struct PQR
{
        struct User_Data *ptr;
};

struct ABC
{
        struct PQR *pqr;
};

struct ABC *abc;

abc = malloc(sizeof(struct ABC));
abc->pqr = malloc(sizeof(struct PQR));

• Step 3 : Point single structure pointer to single dimension array

abc->pqr->ptr = arr;

• Step 4 : Iterate through single dimension array using pointer

for (int i = 0; i < 2; i++)
{
        struct User_Data c;

        c = *++abc->pqr->ptr;

        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

• Step 5 : Free memory after use

free(abc->pqr);
free(abc);

• See full program below

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

struct User_Data {
        int a;
        int b;
};

struct PQR
{
        struct User_Data *ptr;
};

struct ABC
{
        struct PQR *pqr;
};

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct ABC *abc;

        abc = malloc(sizeof(struct ABC));
        abc->pqr = malloc(sizeof(struct PQR));

        abc->pqr->ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                struct User_Data c;

                c = *++abc->pqr->ptr;

                printf("c.a = %d\n", c.a);
                printf("c.b = %d\n", c.b);
        }

        free(abc->pqr);
        free(abc);

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

Pre Increment : Function Call

• *++ptr : Function Call

• ++ptr : Function Call

*++ptr : Function Call

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Define a single pointer and point to array

struct User_Data *ptr;

ptr = arr;

• Step 3 : Iterate array using ++ptr and Pass by Value

for (int i = 0; i < 2; i++)
{
        fun(*++ptr);
}

• Step 4 : Define a function fun which receives a structure from caller

void fun(struct User_Data c)
{
        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

Let us Recall,

• In case of *++ptr

  • ptr is incremented first, then current value of *ptr is assigned

• Hence, in this case

  • ptr is incremented first, then current value of *ptr is passed as arguement to function fun

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

void fun(struct User_Data c)
{
        printf("c.a = %d\n", c.a);
        printf("c.b = %d\n", c.b);
}

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct User_Data *ptr;

        ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                fun(*++ptr);
        }

        return 0;
}

• Output is as below

c.a = 2
c.b = 3
c.a = 4
c.b = 5

++ptr : Function Call

• Step 1 : Define a single dimension array

struct User_Data {
        int a;
        int b;
};

struct User_Data arr[3] = {
        { .a = 0, .b = 1 },
        { .a = 2, .b = 3 },
        { .a = 4, .b = 5 },
};

• Step 2 : Define a single pointer and point to array

struct User_Data *ptr;

ptr = arr;

• Step 3 : Iterate array using ++ptr and Pass by Value

for (int i = 0; i < 2; i++)
{
        fun(++ptr);
}

• Step 4 : Define a function fun which receives a structure pointer from caller

void fun(struct User_Data *c)
{
        printf("c->a = %d\n", c->a);
        printf("c->b = %d\n", c->b);
}

Let us Recall,

• In case of ++ptr

  • ptr` is first incremented, then assigned

• Hence, in this case

  • ptr` is first incremented, then current value of ptr is assigned as argument to function fun

• See full program below

#include <stdio.h>

struct User_Data {
        int a;
        int b;
};

void fun(struct User_Data *c)
{
        printf("c->a = %d\n", c->a);
        printf("c->b = %d\n", c->b);
}

int main(void)
{
        struct User_Data arr[3] = {
                { .a = 0, .b = 1 },
                { .a = 2, .b = 3 },
                { .a = 4, .b = 5 },
        };

        struct User_Data *ptr;

        ptr = arr;

        for (int i = 0; i < 2; i++)
        {
                fun(++ptr);
        }

        return 0;
}

• Output is as below

c->a = 2
c->b = 3
c->a = 4
c->b = 5

See Also

• Current Module

  • Pre Increment with Pointers

• Previous Module

  • Function Pointers

• Next Module

  • Post Increment with Pointers

• Other Modules

  • Basic Equations

  • Basic Arrays

  • Malloc and Pointers

  • Type-Casting and Pointers

  • Functions and Pointers

  • Memcpy and Pointers

  • Const Pointers

  • void Pointers

  • Array of Pointers

  • Pointer to an Array

  • Pre decrement with Pointers

  • Post Decrement with Pointers