C++ objects having arrays

[Iniamyen]

Another frustrating C++ question for anyone who can spare a minute...

I'm trying to create a class which has an array member (contains an array, is this the correct term?) The class has functions make_array() and show_array. The make_array() function just prompts the user for array indices and the filename to be read, and then goes through and creates the array from the file. I have verified my parsing routines and they all work. The show_array() function simply prints the contents of the array to the console using cout.

The problem is that when I tell the object that it has an array in the private section, I have to specify a size for it. If I don't, and just use object_type array_name[] format, it defaults the array to zero size. I want to be able to have the user prompts in the make_array() function define the size of the array, however to even let the thing know I have an array of finite size, I have to specify an actual size at runtime.

I've tried creating an integer variable and saying object_type array_name(variable), and letting the user prompts define the value of the variable, but the compiler does not like this at all.

Any help appreciated!

[doctorgonzo]

You can't dynamically size arrays in C++ (actually, I think there is a way, but it is not pleasant). You have to supply a size at compile time, not later. Obviously, this is a huge pain. You can either set the size at compile time to be larger than any size you think you need (a waste and dangerous if you guess too low), or you can use vectors.

[DrZaius]

Hi Iniamyen,

I havn't done C++ in a while, but as I recall arrays are statically created, so you must have the size set before compiling the code. You might have to use a dynamic data structure like a linked list to store the data.

Edit: doctorgonzo beat me to it.

[Iniamyen]

Yes, I made an exact counterpart to my array code which does a vector, and it works great, but the boss told me he wanted the object to have an array instead (I don't know why.)

Well, as long as I can make it too big, I know generally how many elements I'll need so I can do it that way.

I did not know that it was such a pain to specify array size at runtime. Thanks very much for the help.

[doctorgonzo]

Originally posted by Iniamyen Yes, I made an exact counterpart to my array code which does a vector, and it works great, but the boss told me he wanted the object to have an array instead (I don't know why).

Ah, yes, the "I want it my way even if it doesn't work" method of managing.

[Iniamyen]

I don't know if the array provides any performance advantage for large objects or lots of objects or anything like that. The only advantage that I see to using arrays is that they can be multidimensional. I'm not sure if what I'm doing will end up needing multidimensionality or not. I'm sure the specifics of exactly how things are stored in memory and how the computer accesses different types of containers etc... is very interesting, but I don't have the time to work on that.