a set of N classes?

[schdvir]

Hi

I want to use a set of N classes.
I have a class called "C_weights" which compute and update a set of
weights for function aprroximation.
Now, the user should determine how much functions are needed.
Therefore, If the user needs N functions, I need to call the class
"C_weights" N times.
How should I do this?
I thought maybe to build an array of C_weights, but I'm not sure if its
the right solution.

Thanks, for your help.
Dvir

[Ney André de Mello Zunino]

sc*****@gmail.c om wrote:

I want to use a set of N classes.
Do you mean /n/ classes or /n/ instances of the class /C_weights/?
I have a class called "C_weights" which compute and update a set of
weights for function aprroximation.
Now, the user should determine how much functions are needed.
Therefore, If the user needs N functions, I need to call the class
"C_weights" N times.
How should I do this?
I thought maybe to build an array of C_weights, but I'm not sure if its
the right solution.

That really depends on what you mean by "call the class". Do you mean
you will need to construct /n/ instances of the class, depending on the
user's input? Or do you mean that you will have to invoke a given method
of that class /n/ times? If the former, a dynamically-allocated array or
a vector (preferred) should do just fine. E.g.:

cout << "How many functions? ";
int n;
cin >> n;
vector<C_weight > weightCalculato rs(n);

There you have a collection of /n/ C_weight objects. Is that what you
are looking for?

Regards,

--
Ney André de Mello Zunino

[dvir]

> Do you mean /n/ classes or /n/ instances of the class /C_weights/?

well I dont really understand the differnce between those two options,
so I'll try to describe what I want to do.
This is the interface of the class:

weights.H
---------------

#ifndef WEIGHTS_H
#define WEIGHTS_H

#ifndef WEIGHT
#define WEIGHT

#define DT 0.01

#include "base_functions .H"

typedef struct weight_t
{
float current_value;
float prev_value;
}weight;


class C_weights
{

private:
weight* weights_vec;
public:
C_weights();
~C_weights();
float get_previous_we ight(int i);
float get_current_wie ght(int i);
void update_wieghts( float eta, float noise,base_func tions* functions,
float delta);
bool new_weight(floa t func_value, float delta,int func_num);
//weight wheits_vec[0];
boost::numeric: :ublas::matrix< weight> wghits_mat;
};

#endif
#endif
this class contain all the characteristics of the set of weights which
define a function.
I want to use N functions.
Each function uses different set of weights.
How should I do it?
Can I have a vector of C_weights?
What is the differnce between vector and array?

Thanks.
Dvir

[Cy Edmunds]

"dvir" <sc*****@gmail. com> wrote in message
news:11******** **************@ g10g2000cwb.goo glegroups.com.. .

Do you mean /n/ classes or /n/ instances of the class /C_weights/?
well I dont really understand the differnce between those two options,
so I'll try to describe what I want to do.
This is the interface of the class:

weights.H
---------------

#ifndef WEIGHTS_H
#define WEIGHTS_H

#ifndef WEIGHT
#define WEIGHT

#define DT 0.01

#include "base_functions .H"

typedef struct weight_t
{
float current_value;
float prev_value;
}weight;


class C_weights
{

private:
weight* weights_vec;

I suggest you change this to

std::vector<wei ght> weights_vec;

It will make everything easier.


public:
C_weights();
~C_weights();
// if you need this you also need a copy constructor and assignment
operator. But if you use std::vector you don't need this.
float get_previous_we ight(int i);
float get_current_wie ght(int i);
void update_wieghts( float eta, float noise,base_func tions* functions,
float delta);
bool new_weight(floa t func_value, float delta,int func_num);
//weight wheits_vec[0];
boost::numeric: :ublas::matrix< weight> wghits_mat;
Public data is not usually a good idea. Is this really what you mean?
};

#endif
#endif
this class contain all the characteristics of the set of weights which
define a function.
I want to use N functions.
Each function uses different set of weights.
How should I do it?
See suggestions above. However, if you really just want N sets of weights
you might consider

typedef std::vector<wei ght> t_weight_vec;

This construction corresponds very closely to your problem statement: you
want "N functions" which means "N sets of weights". You can write
convenience functions rather than class member functions to do work on this
type:

// not a member function; just a function -- note first argument
void update_wieghts( t_weight_vec &wv, float eta, float noise, base_functions
*functions, float delta);
Can I have a vector of C_weights?
Sure. std::vector<C_w eights> whatever;

Or:

typedef std::vector<t_w eight_vec> t_weight_mat;
What is the differnce between vector and array?
The names are historical accidents. std::vector can be used for a
geometrical vector but is often used with non-numerical types. On the other
hand std::valarray, which is intended for numerical types and therefore is
much more likely to be a geometrical vector obviously has the wrong name.
The C language construct int x[5]; is usually called an array also.

I suggest you study up on std::vector. It works fine with numerical and
non-numerical types and is easy to use and generally efficient.

Thanks.
Dvir

You're welcome.
Cy