Thread: If String Help

Hey everybody, hadn't came here in a while, but i just got stuck:

Code:

#include <stdio.h>

int main(void)
{
    char answer[0];
    
    printf("\nWhich formula do you want to use?\n");
    scanf("%s", answer);
    
    if (answer=="a")
    {
        printf("You chose a!");
                               
    }
    else
    {
        printf("Else!!!");
        }
    getchar();
    return 0;

}

Even when I type "a", it returns "Else!!!". What's the problem with this?

Code:

#include <stdio.h>

int main(void)
{
    char answer[0];
    char formula1[1] = "a";
    
    printf("\nWhich formula do you want to use?\n");
    scanf("%s", answer);
    
    if (answer==formula1)
    {
        printf("You chose a!");
                               
    }
    else
    {
        printf("Else!!!");
        }
    getchar();
    return 0;

}

This doesn't work either, soz for double post, but it makes sense here.

use strcmp() from string.h.
go and read documentation before asking any question about how to use function!

Originally Posted by Bayint Naung

use strcmp() from string.h.
go and read documentation before asking any question about how to use function!

Code:

#include <stdio.h>
#include <string.h>

int main(void)
{
    char answer[0];
    
    printf("Welcome to Formulum!\n");
    printf("\nWhich formula do you want to use?\n");
    scanf("%s", answer);
    
    if (!strcmp(answer,"a"))
    {
        printf("You chose a!");
                               
    }
    else
    {
        printf("Else!!!");
        }
    getchar();
    return 0;

}

Works great thanks!

I think OP is using gcc. gcc accepts such kind of thing...
Anyway I suggest that OP uses either C89 or C99.
gcc -std=c89 -Wall -pedantic-errors source.c # or -std=c99 for C99

Originally Posted by laserlight

You still should not be writing:

Code:

char answer[0];

This use of a zero length array may be allowed as a compiler's language extension, but is otherwise illegal, and is not intended to be used like this anyway. Rather, put a number greater than 1 (since you also need to account for the null character).

So how do I make it work for like infinite characters, since I don't know what the user is gonna write, for example: user's name.

You have to use dynamic memory allocation.malloc,realloc,calloc,free.
But i think you should master pointer,array,etc first...

Hey I maybe a noob but maybe I can help with this one.


char answer=="a"

you are comparing a string when it should be 'a'

a string is an array of characters, and when you store a string - they are divided into characters

so if i had
char answer[6] = "Hello" ;
it will be like this in memory
'H' 'e' 'l' 'l' 'o' '\0'
Notice that although the length of hello is 5 characters long, I am declaring the variable answer as having 6 elements, because a string of char type in C/C++ must be terminated by a null character.

so when you did
char answer[0] ="a"
number one that is redundant.

Why do that, when you can simply do char
answer = 'a' ?
also when you initialize
char answer[0]="a"
I am surprised that even compiled..the compiler should have told you to declare at least one element, I know this without compiling it, because I did the same thing last year
If you had declared more than one element for answer, then your if statement should have worked.

strcmp should have worked as well

Since others have provided a code for strcmp. I wouldn't
but I hope my explanation on how strings are stored in memory helped .

Originally Posted by ScoutDavid

So how do I make it work for like infinite characters, since I don't know what the user is gonna write, for example: user's name.

Well, the thing is you can't unless you know the length of the maximum string you want to store.

you could do this of course.

char answer[] = "a"
and that would automatically put in a null character for you.

but let say later you want to use a strcat() function to add a string to the array
answer? Well you can't because the length is already defined.
You will get a compiler error or warning at least.

The only way is either to declare a massive amount of element if you are lucky to have enough memory.
Or use dynamic memory allocation - although I haven't tried that yet...

But one thing.. if you start using strings with C++
there is a class called string, to declare string objects.

It is a beauty, and you rarely have to worry about string length, and you never have to worry about the null character!

Originally Posted by Eman

Hey I maybe a noob but maybe I can help with this one.


char answer=="a"

you are comparing a string when it should be 'a'

a string is an array of characters, and when you store a string - they are divided into characters

so if i had
char answer[6] = "Hello" ;
it will be like this in memory
'H' 'e' 'l' 'l' 'o' '\0'
Notice that although the length of hello is 5 characters long, I am declaring the variable answer as having 6 elements, because a string of char type in C/C++ must be terminated by a null character.

so when you did
char answer[0] ="a"
number one that is redundant.

Why do that, when you can simply do char
answer = 'a' ?
also when you initialize
char answer[0]="a"
I am surprised that even compiled..the compiler should have told you to declare at least one element, I know this without compiling it, because I did the same thing last year
If you had declared more than one element for answer, then your if statement should have worked.

strcmp should have worked as well

Since others have provided a code for strcmp. I wouldn't
but I hope my explanation on how strings are stored in memory helped .

Thanks much!


However, I still have a doubt:

Code:

while (!strcmp(answer,password))
    {
        printf("Wrong Password");
        scanf("%s", answer);
          
    }

This does: "while answer equals password"
How do i do: "while answer isn't equal to password"??

Thank you in advance!

For isn't equal, I would change laserlight's == into !=.