Dunamic type converstion. Please help?

[LiquidE_SA]

I've got a problem. I'll get input to my program and I have to determine which type of data that is. Input will occur in a text file and will look similar to this: Add: 41.4 51.8 48.4 22.1 Delete: 84.1 57.4 15.1 etc.... The problem is I have to determine the type of the data that needs to be added to the tree. The tree is a template class. I want to know code that could do the same as the following is supposed to do: typedef T; T = int of T = double; AbstractTree *tree = new BTree; I then want to use type T in the rest of my program. etc. AbstractClass *tree = new BTree; I need this for a project that needs to be in on Monday 20:00(GMT) Your help will be greatly appreciated. Thanks alot

[VaporTrace]

You need something to parse your input with like a char str and extract your numerical into a double. int doesn't do decimal so how do you know if a decimal is in your input? It's a text file input so it's automatically a char going in. atof() and isalnum() would be my first thought or get out your ASCII table if you want to build your own smarter atof() to parse your entire input line at a time. I don't know of anyone that wants to just hand you an answer to copy. Remember the basic purpose of a template it to reduce redundant code differing only in parameter type, allowing the same call with different types. But then again maybe I'm not understanding what you are doing, like are you pulling the entire input file into a buffer or are you grabing input by keyword, space, line ??

[LiquidE_SA]

I'm grabbing input word by word. instead of coding: if (input is numeric) if (input contains '.'){ AbrstrackTree *p = new BTree(); AbrstrackTree *p = new BStarTree(); AbrstrackTree *p = new BPlusTree(); AbrstrackTree *p = new Trie(); } else { AbrstrackTree *p = new BTree(); AbrstrackTree *p = new BStarTree(); AbrstrackTree *p = new BPlusTree(); AbrstrackTree *p = new Trie(); } if (input is char*){ AbrstrackTree *p = new BTree(); AbrstrackTree *p = new BStarTree(); AbrstrackTree *p = new BPlusTree(); AbrstrackTree *p = new Trie(); } I want to do something similar to: typename int T; AbrstrackTree *p = new BTree(); AbrstrackTree *p = new BStarTree(); AbrstrackTree *p = new BPlusTree(); AbrstrackTree *p = new Trie(); I'm trying to find out if there's a way of changing the type of T at run-time

[VaporTrace]

So you're trying to ring my bell because now you are creating ambigious function pointers.

[RichardS]

As far as I can remember once a type is defined that's it. The compiler does the conversion from T to int/double/long/etc. So at run-time there is no T, it as become a known integral type so you can't change it. Also your code above is really strange and does not make much sense. But I really don't get what the real problem is. If you define T as double (as per VaporTrace) then you can set it as an integer or decimal from your input. regards, Rich "Programming today is a race between software engineers striving to build bigger and better idiot-proff programs, and the Universe trying to produce bigger and better idiots. So far the Universe is winning." -- Rich Cook

[LiquidE_SA]

The problem is that the input I an getting can be of any basic data type....int, double,char..etc My data-structure is using templates that is been made at compile-time, but I need the type to change in real time. I think there is a way to do it using a derived class of the template class, but I can't seem to figure it out. I'm sure many people had the same problem before with something like using a STL vector or list, and not knowing what type of data will be stored in the vector, at compile time. Please help!! I hope I explained my problem clearly.....?

[RichardS]

Hi, Ok, the way you could do it is by creating a union. Seeing the you need types int, double and char, just create a union of them all:

typedef union
{
char c;
double d;
int i;
} UTYPES;

This way you can use that for your template class. Now which ever type you need it will be in the union. But remember to be careful how you treat the union. You will also have to do some nifty programming in the template class to get around not being an exact type. The best would be a container class for it so that you can have some control over what values are stored in the union. Hope this helps. :) regards, Rich "Programming today is a race between software engineers striving to build bigger and better idiot-proff programs, and the Universe trying to produce bigger and better idiots. So far the Universe is winning." -- Rich Cook

[LiquidE_SA]

We'll try that. Thanks alot for your help.