if-else statement condition

Hi, i got problem with my coding
i'm using structure array because of the question of my assignment.
So i have testing for many hour already and i'm still stuck.
I want the code just printing the list[0] and list[1] index but it's still printing the list[3] index also, i have found the problem which is my if-else condition does not work..it is still compile but it does'nt work

Code:

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printf("\n--Current Student Information--\n");   
for(int i = 0;i<4;i++){
        if(list[i].name != NULL){
            printf("\nPrintName: %s\nPrintAge: %d\n",list[i].name,list[i].age);
            *numOfCus = *numOfStu + 1;
        }else
            return(*numOfStu);
}

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Please sharing your experience..Thank you so much

Quote:

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Originally Posted by YouMe

I want the code just printing the list[0] and list[1] index but it's still printing the list[3] index

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That is because your loop condition is i < 4 rather than i < 3.

Quote:

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Originally Posted by YouMe

also, i have found the problem which is my if-else condition does not work..it is still compile but it does'nt work

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Probably because you should be using strcmp to compare with an empty string instead. (Or just test if list[i].name[0] == '\0')

Quote:

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Originally Posted by laserlight

That is because your loop condition is i < 4 rather than i < 3.

Probably because you should be using strcmp to compare with an empty string instead. (Or just test if list[i].name[0] == '\0')

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Oh The loop because i entered the structure array info for list[0] and list[1]..so i thought after entering the for-loop and then entering the if-else statement it will return to the main function

it mean when list[i].name is not equal to NULL..it will enter the if-else..so for now the situation list[0],list[1] now have the information
list[2] and list[3] does not have the info...it will printout the list[0] and list[1] and then return to the main function after the if-else is false..
so that's why i stuck..and just now you say using list[i].name[0] == '\0'...still ignored the condition..

O_o

I'm not following.

Are you saying you want the loop to stop looping at the first index that references a "NULL" string?

Soma

ok like this

Situation:
list[0] and list[1] index has the information..already input list[0].name and others..

So,

Code:

---

printf("\n--Current Student Information--\n");   

    for(int i = 0;i<4;i++){       
      if(list[i].name != NULL){           
      printf("\nPrintName: %s\nPrintAge: %d\n",list[i].name,list[i].age);         
      *numOfCus = *numOfStu + 1;       
      }else         
      return(*numOfStu);

}

---

so the first looping will become for list[0] correct?
then check the condition if the list[0].name is not equal to NULL ( it's mean the array is not empty)
It's will enter the if-else when the condition is true becuase list[0].name have string in it..so it's not empty
the print all the Name,Age for the list[0]
Out from the if-else statement

now for list[1]
(doing the same thing)

now for list[2]
Not contain anything, no string...so it's false
so return(numOfCus); will executed to return to the main function..

now my problem is..the code printing all over from list[0],list[1],list[2],list[3]...although list[2] and [3] not contain anything..it still printing but display unknown symbol for list[2] and list[3]

can understand it?

How are you initializing your "name" variables in the "list" struct? An uninitialized character array is not "NULL". Perhaps you need to monitor for a different parameter to determine when the loop should terminate (for instance, initialize "age" to zero and stop the loop when a listing is reached where "age" is equal to zero).

I don't understand the first question...can you give an example what you saying ?^^..i have problem because still new

So, you're saying i should use list[i].age in the condition?

Post the smallest and simplest compilable program that demonstrates the problem.

It still the same although the printf is different..customer instead of student..don'nt mind that

Code:

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struct Info {
    char name[70];
    int age;
};

int addStudents(Info list[],int *numOfStud){
    printf("--Now in addStudents Function--\n\n");
    *numOfStud = 0;

    for(int i = 0;i<2;i++){
        if(list[i].name != NULL){
            printf("\nIndex [%d]\n",i);
            printf("Name: ");
            scanf("%s",&list[i].name);
            printf("Age: ");
            scanf("%d",&list[i].age);
          }
    }
   
    printf("\n--Current Students Information--\n");
    for(int i = 0;i<3;i++){
        if(list[i].name != NULL){
            printf("\nPrintName: %s\nPrintAge: %d\n",list[i].name,list[i].age);
            *numOfStud = *numOfStud + 1;
        }else
            return(*numOfStud);
    }
}

void main(){
    Info list[10];
    int numOfStud;


    printf("\n--Now in Main--\n\n");
    addStudents(list,&numOfStud);
    printf("\n--Back to Main--\n\n");
    printf("Number of Students: %d\n\n",numOfStud);


    system("pause");
}

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Output:
Attachment 11785

Just input two index only..it still printing until 3 index

O_o

Variables aren't "zeroed" by default; you are checking for an assumed value when it is unknown.

o_O

Actually, that's my bad. The above is true, but you are checking the address of an array on the stack so it will never be null.

Set the values to a defined type and check for a "zero length string" as laserlight suggested earlier.

Soma

Quote:

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Originally Posted by phantomotap

O_o

Variables aren't "zeroed" by default; you are checking for an assumed value when it is unknown.

o_O

Actually, that's my bad. The above is true, but you are checking the address of an array on the stack so it will never be null.

Set the values to a defined type and check for a "zero length string" as laserlight suggested earlier.

Soma

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I'm not understand, can you show where is it to correct it?..i mean an example

This line has a warning in MinGW GCC

Code:

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scanf("%s",&list[i].name);

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Code:

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warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char (*)[70]' [-Wformat]|

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I had to edit your code to get it to compile with a C Compiler.
It is likely that your are using an C++ Compiler.

Code:

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

typedef struct Info {
    char name[70];
    int age;
} Info;

---

NOTE: main returns a int
Read the FAQ FAQ > main() / void main() / int main() / int main(void) / int main(int argc, char *argv[]) - Cprogramming.com

Hint: An array name is not like a normal variable name.

Tim S.

yes i'm using MVisualStudio2010...

but i thought the main problem here is the if-else condition right?

Quote:

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Originally Posted by YouMe

yes i'm using MVisualStudio2010...

but i thought the main problem here is the if-else condition right?

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The reason you are getting garbage out of list[i].name is because you never put anything valid into that location.

Note: The if/else likely has problems, also.

Tim S.

haha, so complicated...
my head is so hot right...it's been 12 hour...haha
i'm still stuck in that function.....i still have 7 other function to go...i can't continue to other function when i'm stuck because this function is the main problem..

Thank you for responding you guys...i appreciate..it' is really my fault because i can't understand what you trying to say to fix my code....
i'm still new in this c-language..

Instead of

Code:

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scanf("%s",&list[i].name);

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Use

Code:

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scanf("%s",list[i].name);

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In the future, remember an array name is the address of the array; so no need most of the time to put an address operator (&) in front of it.

Tim S.

Quote:

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Originally Posted by YouMe

I'm not understand, can you show where is it to correct it?..i mean an example

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If you declare a variable like

Code:

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int x;

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the compiler just allocates enough memory to store a value of this type, but it doesn't clear the memory. So whatever value is stored at this memory location is still there (probably just garbage).

Code:

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int x = 0;

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initializes the variable x to 0 and then you can be sure that this value stays there as long as you don't change it.

The problem in your code is that

Code:

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if(list[i].name != NULL)

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compares the pointer "list[i].name" to the pointer "NULL" and the result is always true because all elements of list have a valid memory address and thus they are unequal to NULL. What you want is to compare the value the pointer "list[i].name" points to to a value which denotes an empty string (usually '\0' as the only character in the string). But you have to initialize your list-array to be able to do this.

I also suggest reading a tutorial about pointers, arrays and strings.

Bye, Andreas