Vector of Templates Problem

I want to create a vector of templates but I'm getting 2 linker errors.
I am doing the following :

template<typename T>
int main()
{
vector<T> exp;
return 0;
}

I really need to store elements of different types in the same vector. Please help thank you.

http://stackoverflow.com/questions/1...tor-array-in-c

Quote:

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Originally Posted by VictorN

http://stackoverflow.com/questions/1...tor-array-in-c

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I don't know anything about boost so can u provide code on how to use it to make vector which can hold any data type using the code I mentioned in the post

Quote:

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I really need to store elements of different types in the same vector.

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Why? What are you trying to accomplish? c++ is a strongly typed language so mixing types within the same variable (whether a container or basic type) is not really supported by the languauge.

If these different types are related - eg different derived classes from a base class then this is fairly simple. If the types are not related then it is a whole different scenario. The easiest way to do this is to use Boost any or Boost variant. If you're not using Boost then you'll need to 'roll your own'. This is doable but non-trivial.

Quote:

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Originally Posted by Fateslayer

I don't know anything about boost ...

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I don't it either...
The main point is you cannot "make vector which can hold any data type". Period.
You could, however, make vector which can hold pointers to "any data type" if you cast these pointers to something like void*

Quote:

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Originally Posted by VictorN

I don't it either...
The main point is you cannot "make vector which can hold any data type". Period.
You could, however, make vector which can hold pointers to "any data type" if you cast these pointers to something like void*

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and some way of knowing to what data type to re-cast these void* pointers when they are needed to be used.

Quote:

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Originally Posted by 2kaud

and some way of knowing to what data type to re-cast these void* pointers when they are needed to be used.

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Tell me how please with the code example

Quote:

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Originally Posted by Fateslayer

Tell me how please with the code example

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Possibly in the next couple of days when I have some time I'll take a look.

But you haven't answered my question in post #4. Why do you want to this? What are you trying to accomplish?

Quote:

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Originally Posted by Fateslayer

template<typename T>
int main()
{
vector<T> exp;
return 0;
}

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templatizing main() ? ? ?

Quote:

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Originally Posted by OReubens

templatizing main() ? ? ?

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That's how we create templates I guess but I need a vector which supports all data types and can store them

Quote:

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Originally Posted by Fateslayer

... I need a vector which supports all data types and can store them

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Then, please, explain why you need "a vector which supports all data types".
What are these types?

And, BTW, what linker errors did you get?

Quote:

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Originally Posted by Fateslayer

That's how we create templates I guess but I need a vector which supports all data types and can store them

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main() cannot be used with a template - hence the errors!

but you still haven't explained why and what you are trying to achieve. :(

Quote:

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Originally Posted by 2kaud

main() cannot be used with a template - hence the errors!

but you still haven't explained why and what you are trying to achieve. :(

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I think it's okay to use templates with main() function. I don't know if there is any limitations on where I can use it.
Anyways I'm trying to read a mathematical expression into a vector. First I take the expression into a string for example
(5+5)*9
As you can see there are two data types in this expression the first is double or int for numbers and second is char for operators like +, -, %, (,/ etc. Copying the string into vector is not a problem nor converting the string numbers into double. The problem is vector can only hold data of same type hence I was trying to use templates with vector so that I can use it to store both numbers and characters. That's all I wanna do to store elements of different data types into single vector

What you are trying to do is parse an expression and then evaluate it. There are various ways of doing this in c++ but none require a vector that holds different types.

Have a look at
http://stackoverflow.com/questions/6...pressions-in-c
http://stackoverflow.com/questions/1...ression-in-c-c
http://stackoverflow.com/questions/1...ression-parser
http://www.speqmath.com/tutorials/ex...cpp/index.html

and associated links

There are also numerous other internet sites that explain expression parsing and evaluation - just do a search.

Quote:

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Originally Posted by 2kaud

What you are trying to do is parse an expression and then evaluate it. There are various ways of doing this in c++ but none require a vector that holds different types.

Have a look at
http://stackoverflow.com/questions/6...pressions-in-c
http://stackoverflow.com/questions/1...ression-in-c-c
http://stackoverflow.com/questions/1...ression-parser
http://www.speqmath.com/tutorials/ex...cpp/index.html

and associated links

There are also numerous other internet sites that explain expression parsing and evaluation - just do a search.

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Thank you so much. I really appreciate it so that means vector which can hold any data type will maybe come in the future versions of c++.