problem in pass by reference

**personal12** · 09-24-2011

solve

**laserlight** · 09-24-2011

This:

Code:

void main()

should be:

Code:

int main()

Now, your change function takes a pointer to int as an argument. Therefore, in the main function, you cannot pass number, but rather should pass &number to the change function. Note that we more typically refer to "pass by reference" as using a reference parameter, not a pointer parameter, even though passing a pointer has call by reference semantics with respect to what the pointer points to.

Incidentally, what is this program supposed to do?

**personal12** · 09-24-2011

Actually i have a assignment that asking me to get the array from a function then cout at another function.The user have to choose switch in order to get to the function
if i add & to the number.
[code]
case 2:change(&number);
[code]

it will give me address like-832455433;

**MK27** · 09-24-2011

Originally Posted by personal12

The user have to choose switch in order to get to the function
if i add & to the number.

Maybe you are confused by something about &.

When prefixed to an existing variable, & is the address of operator, eg:

Code:

int x, *p = &x;

When used with a function parameter or variable declaration, & indicates a reference:

Code:

int x, &p = x;
void somefunc(int &n);

Also note that this:

Code:

void change(int number[])

is equivalent to this:

Code:

void change(int *number)

which is why using &number works -- it creates a pointer, not a reference. As laserlight says, these are very similar things, but do confuse them as the syntax is non-compatible.

**Elysia** · 09-24-2011

If you are trying to pass an array to another function, then (one of) the correct syntax(es) would be:

Code:

int myarray[arbitrary_size];
myfunc(myarray);

Very import exception here: do not use & on the array.

Code:

void myfunc(int * myarray)

Now, you treat myarray as an array and print its contents.

**laserlight** · 09-25-2011

Sorry, but your code looks incoherent considering what you stated as your assignment.

What do you mean by "the user have to choose switch in order to get to the function"?

**AndrewHunter** · 09-25-2011

Merge posts Laser?

EDIT: Maybe you should consider this one as well. I think we have a homework spammer.

**personal12** · 09-25-2011

never mind .But please can someone tell me how come if i press 2 it will give me -89245435345 and how i can fix this.

**AndrewHunter** · 09-25-2011

Originally Posted by personal12

never mind .But please can someone tell me how come if i press 2 it will give me -89245435345 and how i can fix this.

Don't press 2.......

**personal12** · 09-25-2011

you are not answering the question

**Salem** · 09-25-2011

> case 2:change(&a);break;
Passes a pointer to ONE integer.

> void change(int number[])
Expects a pointer to TWO integers.
So yes, there is garbage to be found.

**laserlight** · 09-25-2011

Originally Posted by personal12

never mind .But please can someone tell me how come if i press 2 it will give me -89245435345 and how i can fix this.

It gives you that because a was not initialised, so when you pass a pointer to a, dereferencing the pointer gives you garbage. Furthermore, number[1] is incorrect because a is a lone variable.

I cannot tell you how to fix this because I do not know what you are trying to do. Sure, you have stated what your assignment is about, but this does not tally with what I expect you to have written. Your change function does not change anything, so it has a lousy name. It looks like it is intended to print the first two elements of an array, yet you are trying to use it with a lone int variable.

Originally Posted by personal12

you are not answering the question

You are not answering my questions either.

**AndrewHunter** · 09-25-2011

Originally Posted by laserlight

It gives you that because a was not initialised, so when you pass a pointer to a, dereferencing the pointer gives you garbage. Furthermore, number[1] is incorrect because a is a lone variable.

I cannot tell you how to fix this because I do not know what you are trying to do. Sure, you have stated what your assignment is about, but this does not tally with what I expect you to have written. Your change function does not change anything, so it has a lousy name. It looks like it is intended to print the first two elements of an array, yet you are trying to use it with a lone int variable.

You are not answering my questions either.

As least someone has a sense of humor....

**personal12** · 09-25-2011

what do you mean by garbage to be found

**AndrewHunter** · 09-25-2011

Originally Posted by personal12

what do you mean by garbage to be found

Did you even look at the code you posted? You declare a as an int and then pass it to your function as an array. Pay attention to what Laser is saying.

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