## Reading a file of unknown length using dynamic arrays etc.

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### Reading a file of unknown length using dynamic arrays etc.

This is the link to my homework.
http://cis.poly.edu/cs1124/Homework/hw02/hw02.htm
I am having trouble understanding how I would do this. My friend leaned only vectors and knows somewhat how to do this in vector but I'm very lost as to how to do this with arrays. I am only allowed to use arrays. Can anyone assist me with this? Thanks.
Guest

Sorry, username thing didn't work. Please note that I'm not asking anyone to solve this for me, just if they can help me understand how to start this thing, or how to go about doing this.
user125

Posts: 3
Joined: Mon Oct 06, 2003 12:33 pm

Read the documentation on realloc(). That, the description of the assignment and hard thinking should get you started.

Alvaro
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Location: NY, USA

we can't use that function.
user125

Posts: 3
Joined: Mon Oct 06, 2003 12:33 pm

Are you familiar with pointers as arrays?
ie,
int *myAr = new int[50];

if, later on, you need a larger array
int *newAr = new int[100];
// copy myAr[i] to newAr[i] for all i in myAr
delete [] myAr;
myAr = newAr;

Then your array gets a size of 100. Are you allowed to do this?

Wizard

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Location: ON, CA

### making sure

hey thanx for the response i appreciate it!

i can't assign a global / local constant so i don't know if i can use your commands, but then again i am a newbie when it comes to C++ and your code may just be the one i need

i did ask my professor for some tips and he said what i had to do was copy the array and increase the size of the array by a certain number allowing space for more information....
will this command do that?? because i do know using the new command is vital to this program...... i just don't know how to use it in the right way......

but either way thanx for the input
user125

Posts: 3
Joined: Mon Oct 06, 2003 12:33 pm

user125 wrote:we can't use that function.

I didn't say that you should use realloc(). I said that you should read the documentation for it. It explains how a new block of memory is allocated if needed and the content is copied.

Alvaro
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Joined: Mon Sep 22, 2003 4:57 pm
Location: NY, USA

### Re: making sure

user125 wrote:hey thanx for the response i appreciate it!

i can't assign a global / local constant so i don't know if i can use your
<snip>
Dwuh? What else is there besides global and local constants?

Anywho, you don't need a constant, you need a variable that tracks the size of your array. It can be either global or local, it's up to you.
You should have no problem using the code that I posted earlier, if you take the time to understand it. It looks to me like that's exactly what your teach wants you to do.

Wizard