template class

[renurecht]

Hi... pls help to guide me how to do the below question. I have done the coding but my program is doesn't work.

QUESTION:

Given the template Pair<T1, T2>, discuss how you can represent
the following information. Try to declare a corresponding Pair object, and show the
C++ code to store and retrieve the information.
a. Name and age of a person. E.g. ( “Uncle Soo”, 21 ) , ( “Yoda” , 812 ) ,
( “Harry Potter” , 18 )
b. Length and resistance of a wire. E.g. ( 15cm, 0.15ohm ) , ( 100cm, 2.15ohm)
c. Position and color of a pixel (a pixel is a “dot” on your computer screen).
Position is represented as integer X- and Y- coordinate, with the top left corner
as the origin. E.g. ( 3, 12, Green) , (302, 516, Red) etc. You can assume there
are only three colors: Red, Green and Blue.
There are quite a number of alternatives for (c) other than using Pair<T1, T2>.
Suggests a few other solutions and compares them with using the Pair template class.

PROGRAM:

#include <iostream>
using namespace std;

template <typename T1, typename T2>
class pair
{
private:
T1 _first;
T2 _second;

public:
pair(T1 a, T2 b) : _first(a), _second(b) {}

T1 getFirst() const {return first;}
T2 getSecond() const {return second;}
};

template <typename T1, typename T2>
class pair(T1 a, T2 b)
: _first(a), _second(b)
{}

template <typename T1, typename T2>
T1 getFirst() const
{return _first;}

template <typename T1, typename T2>
T2 getSecond() const
{return _second;}

int main()
{
pair<char*, int*> example("Harry Potter", 18);
}

[Airslash]

What your teacher is trying to learn here , is the basic use of template classes.

Template classes provide a common way of defining functions and methods in handeling the data that is represented/stored inside the class.
But instead of writing a class for every possible combination of types, a template is used that allows you to declare it only once, and then change the types to what you need at any given time.

So in your example you can use the code of the template class and create the examples listed in the question.

It's a bit hard for me to explain this over the Internet, as i normally explain stuff like this face to face with demonstrations, but I suggest you google a bit into C++ templates to get the general info regarding them, and i'm sure your question will becomes more clearer then

[weaknessforcats]

You have various syntax errors in this code. This is the corrected code with comments. It compiles and links but it's up to you to see if it works.

#include <iostream>
//weaknessforcats: There is a pair class in std. The compiler sees your pair class as a redeclaration and gives an error. 
//using namespace std;
 
 
template <typename T1, typename T2>
class pair 
{
private:
T1 _first;
T2 _second;
 
public:
pair(T1 a, T2 b) : _first(a), _second(b) {}
 
T1 getFirst() const {return first;}
T2 getSecond() const {return second;}
};
//
//weaknessforcats:this constructor is already in the pair class.
//template <typename T1, typename T2>
//class pair(T1 a, T2 b) 
//: _first(a), _second(b)
//{}
//weaknessforcats:this method is already in the pair class.
 
//template <typename T1, typename T2>
//T1 getFirst() const
//{return _first;}
//weaknessforcats:this method is already in the pair class.
//template <typename T1, typename T2>
//T2 getSecond() const
//{return _second;}
 
int main()
{
pair<char*, int> example("Harry Potter", 18);
 
//weaknessforcats: 18 is not a pointer to an int. See above.
//pair<char*, int*> example("Harry Potter", 18);
}