"Dave Theese" <ch**********@yahoo.com> wrote in message
news:KUa7b.14665$QT5.9944@fed1read02...
Hello all,
I'm trying to get a grasp of the difference between specializing a
function template and overloading it. The example below has a primary template, a
specialization and an overload. Note that the overload is identical to
the specialization except, of course, for the missing "template <>".
I don't know if my questions will be a bit too broad or not, but I thought
I'd give it shot... When is overloading preferable to specialization?
When is specialization preferable to overloading? What is the intended
conceptual difference between the two? Any other guidance on other things
I need to know but don't know enough yet to even ask?
Thanks everyone - this group has been an invaluable resource to me and I
sure appreciate the time of those who have so generously assisted me!
Thanks,
Dave
#include <iostream>
using namespace std;
struct foo
{
int data;
bool operator<(const foo &rhs) const
{
return data < rhs.data;
}
};
template <typename T>
const T &my_max(const T &a, const T &b)
{
cout << "Point 1" << endl;
return (a < b) ? b : a;
}
template <>
const foo &my_max(const foo &a, const foo &b)
{
cout << "Point 2" << endl;
return (a < b) ? b : a;
}
const foo &my_max(const foo &a, const foo &b)
{
cout << "Point 3" << endl;
return (a < b) ? b : a;
}
int main()
{
foo a = {5};
foo b = {10};
// Yields "Point 3" as non-templates are
// preferred.
cout << my_max(a, b).data << endl;
return 0;
}
I am not so clear about your question but here goes. I am using simple
examples
to explain the concepts.
Use composition ( has-a relationship,embedded objects ) over inheritance
(i.e specialisation of a base class).
If there are many related classes differing in the parameters only by the
type, then use templates.
Use operator or function overloading as a last resort.
As an example the sign plus can mean binary addition eg 4 + 7 or string
concatenation or adding
two graphic figures together depending on your program or class.
Thus in this case the plus sign token is an overloaded operator.
As an example for function overloading, lets say for a function
AverageOf3Numbers(param1, param2, param3 ,...)
where average can mean mean or median.
The AverageOf3Numbers( totalof3Numbers) function divides the param1 by 3 to
get the average, as in mean case;
in the other case,the median interpretation of average, all 3 numbers are
passed into the function as in,
AverageOf3Numbers(3 , 5, 8) function does a integer comparison and gives 5
as the median(average).
That is in your class definition, there are two AverageOf3Numbers( ) methods
declared.
However, if you just want to have one interpreation of the meaning of
average , as mean, but the types of the parameters differ,
use a template.
AverageOf3Numbers(integer1, integer2, integer3) ; AverageOf3Numbers(float1,
float2, float3) etc
Use a template class.
As an example of operator-loading, You can write your own complex nos. class
to add , subtract, divide and multiply
complex nos. In this class, all "+", "-", "*" and "/" will be overloaded ,
the methods will be written by you.
First check with a C++ standard book and a STL library book before writing
your own classes. The STL is template-based
and already has many useful methods , functions,functors you can use etc
Regards,
Govin
