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Protoman wrote:
> And, John, here's my program updated to your advice:
>
> #include <iostream>
> #include <cstdlib>
> #include <cmath>
> using namespace std;
>
> ...
> template <class T>
> T harmonic_mean(T& num,T& num2,T& num3,T& num4,T& num5)
> {
> const static T ret=(5/(1/num+1/num2+1/num3+1/num4+1/num5));
> return ret;
> }
>
> int main()
> {
> for(;
> {
> long double num;
> long double num2;
> long double num3;
> long double num4;
> long double num5;
> cout << "Enter five numbers: " << endl;
> cin >> num >> num2 >> num3 >> num4 >> num5;
> cout << "Here's the average: " << fixed << mean<long
> double>(num,num2,num3,num4,num5) << endl;
> cout << "Here's the quadratic mean: " << fixed << harmonic_mean<long
> double>(num,num2,num3,num4,num5) << endl;
> cout << "Here's the harmonic mean: " << fixed << quadratic_mean<long
> double>(num,num2,num3,num4,num5) << endl;
> cout << "Here's the standard deviation: " << fixed << std_dev<long
> double>(mean<long double>(num,num2,num3,num4,num5)
> ,num,num2,num3,num4,num5) << endl;
> }
> system ("PAUSE");
> return 0;
> }
>
> Is there anyway I can make it clearer und more precise und concise, not
> to mention more efficient?

The program should validate its inputs. For example, if the user enters
a 0 as one of the numbers that the program asks for, what is likely to
happen when the program calculates their harmonic mean?

Also, I don't see any benefit from using template functions. On the
contrary, by having to instantiate these routines for a float, when the
program already has instantiated them for a double, provides no added
benefit and simply bloats the code. A set of non-template functions
accepting doubles would seem to make a lot more sense.

Greg

When I say "generalize", I mean, for all the different types of means;
I'm not very good at STL.

OK, I tried it, but it doesn't compile; here are the errors:

C:\Dev-Cpp\average3.cpp In function `T Mean(const std::vector<T,
std::allocator<_CharT> >&)': expected `;' before "i"
11 C:\Dev-Cpp\average3.cpp `i' undeclared (first use this function)
C:\Dev-Cpp\average3.cpp In function `T Mean(const std::vector<T,
std::allocator<_CharT> >&) [with T = float]': instantiated from here
11 C:\Dev-Cpp\average3.cpp dependent-name `
std::vector<T,std::allocator<_CharT> >::const_iterator' is parsed as a
non-type, but instantiation yields a type
11 C:\Dev-Cpp\average3.cpp say `typename
std::vector<T,std::allocator<_CharT> >::const_iterator' if a type is
meant

I wonder what's wrong? Hope this helps!

"Protoman" <> wrote in message
news: oups.com...
> Hey, is this program right? It calculates the average, harmonic mean,
> quadratic mean, and the standard deviation for two numbers. Can you
> proofread it for me?
> Here it is:
>
> #include <iostream>
> #include <cstdlib>
> #include <cmath>
> using namespace std;
>
> template <class T>
> class avg
> {
> public:
> T operator()(const T& num, const T& num2)const
> {
> T ret=((num+num2)/2);
> return ret;
> }
> T operator()(const T& num, const T& num2, int x)const
> {
> T ret=(sqrt(pow(num,2)+pow(num,2)));
> return ret;
> }
> T operator()(const T& num, const T& num2,int x,int y)const
> {
> T ret=(2/(1/num+1/num2));
> return ret;
> }
> operator T()const{return static_cast<T>(value);}
> private:
> T value;
> };
>
> template <class T>
> class Stat
> {
> public:
> T operator()(T avg,const T& num,const T& num2)const
> {
> T ret=num-avg;
> T ret2=num2-avg;
> T ret3=(pow(ret,2)+pow(ret2,2)/2);
> T ret4=sqrt(ret3);
> return ret4;
> }
> operator T()const{return static_cast<T>(value);}
> private:
> T value;
> };
>
> int main()
> {
> for(;
> {
> long double num;
> long double num2;
> avg<long double> Avg;
> Stat<long double> StdDev;
> cout << "Enter two numbers: " << endl;
> cin >> num >> num2;
> cout << "Here's the average: " << fixed << Avg(num,num2) << endl;
> cout << "Here's the quadratic mean: " << fixed << Avg(num,num2,0) <<
> endl;
> cout << "Here's the harmonic mean: " << fixed << Avg(num,num2,0,0) <<
> endl;
> cout << "Here's the standard deviation: " << fixed <<
> StdDev(Avg(num,num2),num,num2)
> << endl;
> }
> system ("PAUSE");
> return 0;
> }
>
> Also, is there anyway I can make it so StdDev can use Avg's arguments
> so I don't need StdDev to have copies of Avg's arguments? And is there
> anyway I can make Avg and StdDev have variable numbers of paramaters; I
> don't want to recompile everytime I want to do more (or less) numbers?
> Thanks a lot.
>

You can use classes to make your statistic work with any number of samples.
For instance (unchecked):

class sample_mean
{
private:
unsigned m_count; // number of samples
double m_sum_x1; // sum of samples
public:
sample_mean() : m_count(0), m_sum_x1(0.0) {}
unsigned n() const {return m_count;}
double xbar() const // no check for 0 samples
{
return m_sum_x1 / m_count;
}
template <typename T>
sample_mean &operator () (T x)
{
++m_count;
m_sum_x1 += static_cast<double>(x);
return *this;
}
void clear()
{
m_count = 0;
m_sum_x1 = 0.0;
}
};

You use it like this:

sample_mean m;
m(1.2)(3.6)(-0.4);
std::cout << m.xbar() << '\n';

--
Cycho{HHR}
http://home.rochester.rr.com/cyhome/

I want to do it w/ functions and STL.

I'm always getting an error on the function's for loop; keeps saying i
is undeclared.

Protoman wrote:
> I want to do it w/ functions and STL.

I'd suggest getting a good book on STL, then. Stroustrup's _C++PL_
gives an overview of the STL, and _The C++ Standard Library : A
Tutorial and Reference_ by Nicolai M. Josuttis goes into greater depth.

Cheers! --M

Where can I buy that; at Borders?

"mlimber" wrote:
>I'd suggest getting a good book on STL, then. Stroustrup's _C++PL_
>gives an overview of the STL, and _The C++ Standard Library : A
>Tutorial and Reference_ by Nicolai M. Josuttis goes into greater depth.

And then "Protoman" wrote:
>Where can I buy that; at Borders?

Somebody who claims to be "a bloody Cal State professor!!!!" (sic) and
"the asst. head of systems programming in the R&D Dept." (sic) where
"We're calculating thruster angles for a prototype ion drive engine."
needs to ask where to buy a well known book from a well known
publisher? The plot thickens ...

Roberto Waltman

[ Please reply to the group, ]
[ return address is invalid. ]

Why are you doing this to me?!!!!!!!!!!!? I'm just asking if you know
if Borders *stocks* that book?!!!!? Let's go back to the original
topic. Please, I beseech you!!!!