How to merge 2 strings ?

[kikloo]

Hi.

I am trying to merge 2 chars. in C but i don't know how to do it.

My code:

char dd[1], aa[2];

dd[0] = "2";
dd[1] = "3";

aa[] = dd[0] + dd[1];

So it aa[] should show: 23 but it gives error. Maybe i am doing it wrong. Please help. Also this is just demo code, i am actually inputting the values of dd[0] and dd[1] from user using getche() function

Thanks.

[devnar]

char dd[1];

That's wrong. You're allocating memory for only one character. Should be dd[2].

aa[] = dd[0] + dd[1];

This statement adds the ASCII values of '2' and '3'. So your result will be 50(ASCII value of 2) + 51(ASCII value of 3). And the result can't be just assigned to an entire array.

If you just wanna merge two chars, you can use:

aa[0] = dd[0];
aa[1] = dd[1];

But I'm not sure if that's what you're looking for. Maybe more info about what you're trying to do would help.

[Aia]

You use the standard C functions strcat()

[kikloo]

Hi,

I am using a custom function in which I have made so that the user can input only 1 char. and that is also just a numeric char. so meaning that user can only enter from 0 to 9.

I am doing like following:

char dd[2];

dd[0] = getinp(); // say user enetered 2
dd[1] = getinp(); // say user enetered 3

Now I have to merge the both values so that it becomes 23 and I can check whether the value is less than 30 or not. How to achieve this ?

If i could just do the following:

aa = dd[0] + dd[1]; // aa will then have 23
if (aa > 30)
{
printf ("Value should not be more than 30");
}
else
{
printf ("Thanks");
}

This is really what I am trying to do.

I am using a custom function becuase it does'nt allows a user to enter anything else other than numbers.

Thanks

[Murtan]

If dd[0] and dd[1] contain the character they entered, the character is NOT the numeric value. (For example in ASCII '0' is 48)

So if the example is dd[0] = '2' and dd[1] = '3' then aa = dd[0] + dd[1]; would give aa the value 50 + 51 or 101.

If you want the numeric value I usually do something like (dd[0] - '0') which in our case would be 2.

So if we did that as we went, we could write

aa = (dd[0] - '0') + (dd[1] - '0')

There, now aa is 2 + 3 which makes aa 5. (wait, didn't you say it should be 23? maybe I missed something.)

I guess I could have done:

aa = 10 * (dd[0] - '0') + (dd[1] - '0')

That would be 23.

You could probably even do it without the array of characters (unless you needed them for something else):

aa = (getinp() - '0');
aa = 10 * aa + (getinp() - '0');

[kikloo]

Hi,

When I added the line:

aa = 10 * (dd[0] - '0') + (dd[1] - '0');

It gives me error:
Lvalue required

What does that means ?

Thanks.

[ArkM]

char onetwo[3]; /* for one, two, zero chars */
char one, two;
one = getche();
two = getche();
onetwo[0] = one; /* array indicies started from 0 */
onetwo[1] = two;
onetwo[2] = '\0'; /* c-string terminated zero byte */
/* Now you have well-formed c-string */
printf("echo: %s\n",onetwo);

Remember: a single char is not a string in C, a c-string is an array of chars with zero byte at the end of its contents.

[kikloo]

HI,

I still don't get it. Please help me merge the string or chars. so that I can go ahead with the program

I am a php and VB programmer and its very easy to do this task in those languages.

VB: a = a & b
php: a = a . b;

What the syntax to do it in C ?

Arrrgh.

[Murtan]

Your original program declared aa as an array of characters:

char dd[1], aa[2];

In your most recent post, you treated aa as an integer:

aa = dd[0] + dd[1]; // aa will then have 23
if (aa > 30)

So I did too. It is not permitted to assign to the array.

Change your declaration to:

char dd[2];
int aa;

[Aia]

>What does that means ?
It means you need to learn a little be more about array of chars and what they represent.
As far as the compiler is concerned aa is not a proper variable to re-assign the kind effect resulted from 10 * (dd[0] - '0') + (dd[1] - '0')

one = getche();
two = getche();

No reason to use a non-portable function when getchar() could have do.

[Murtan]

The 'syntax' question you were ask would be easy to answer if you had 2 strings instead of 2 characters.

In C, you make your own strings if you're taking input one character at a time.

If you wrote:

char dd[3];
dd[0] = getinp();
dd[1] = getinp();
dd[2] = '\0';

Now dd is a real C string. If you wanted to assign it to another string (of sufficient size or bad things happen) you could strcpy(otherstring, dd); But your problem description implied that you don't really need the string, you want the number that it would represent (which is why my previous posts look like they did.)

[ArkM]

No reason to use a non-portable function when getchar() could have do.

Yes, of course, but there is getche in the original post.
Let him/her shoot him/herself in the foot ;)...

[somnathsarode]

hi if u want to merge two strings
then there is readimade function in file
"string.h" name as "strcat"
the function gives concatnation or
merging of two srings

[kikloo]

Hi,

Its confusing me. I am new to this. Help me out! Can't someone help me fix my program so I can achieve what i want to do ? It will be highly appericiated. 2 days I have done several experiments to just merge the things i have already tried strcat, strcpy and what not but its not working. Help me! Please.

Thanks.

[Murtan]

You have been given several suggestions. I haven't seen anything that you've tried, all I've seen are comments that it isn't working -- and I followed those up with what was wrong and I thought I told you how to fix it.

Post the code as it now exists and please confirm whether you want a string with the two characters in it ("23"), or the numeric value of the number formed by the two characters (23). If you want to perform a numeric comparison (say to see if the value they entered was < 30) then you need the numeric value.

Please enclose your code in code tags with a language specifier:
[code=c] /* Your code here */

[/code]

PS- It may have felt like 2 days, but your first post was 13 hours ago.