About for_each usage

[fgh.vbn.rty]

I'm having problems setting up the functors to use for_each. Here's an
example:

class A {
public:
void getName() { return name; }
private:
string name;
};

class B {
public:
vector<intgetId s { return vi; }
A& getA(int idx) { return vA.at(idx); }
void bfunc();
private:
vector<AvA;
vector<intvi;
}

class C {
public:
void cfunc();
private:
B b;
}

void B::bfunc()
{
// populate vi
for(int i=0; i<vi.size(); ++i) {
cout << vA[i].printName() << endl;
}
}

void C::cfunc()
{
// populate vi
vector<intvc = b.getIds();
for(int i=0; i<vc.size(); ++i) {
A& a = getA(vc[i]);
cout << a.getName() << endl;
}
}

Here vA is just a vector of As and vi is a vector of integers that
index into vA. Let's suppose that vA and vi are populated
appropriately. All I'm trying to do is to execute a particular
function on a subset of the As.

I have three questions:
1) How do I replace the for loop in bfunc with a for_each?
2) How do I replace the for loop in cfunc with a for_each?
3) How would I do this using the Boost.Lambda functions?

Thanks.

[Ivan Novick]

On Jul 2, 3:27*pm, fgh.vbn....@gma il.com wrote:

I'm having problems setting up the functors to use for_each. Here's an
example:

class A {
public:
* * void getName() { return name; }
private:
* * string name;

};

class B {
public:
* * *vector<intgetI ds { return vi; }
* * *A& getA(int idx) { return vA.at(idx); }
* * *void bfunc();
private:
* * *vector<AvA;
* * *vector<intvi;

}

class C {
public:
* * *void cfunc();
private:
* * *B b;

}

void B::bfunc()
{
* *// populate vi
* *for(int i=0; i<vi.size(); ++i) {
* * * * cout << vA[i].printName() << endl;
* *}

}

void C::cfunc()
{
* *// populate vi
* *vector<intvc = b.getIds();
* *for(int i=0; i<vc.size(); ++i) {
* * * * A& a = getA(vc[i]);
* * * * cout << a.getName() << endl;
* *}

}

Here vA is just a vector of As and vi is a vector of integers that
index into vA. Let's suppose that vA and vi are populated
appropriately. All I'm trying to do is to execute a particular
function on a subset of the As.

I have three questions:
1) How do I replace the for loop in bfunc with a for_each?
2) How do I replace the for loop in cfunc with a for_each?
3) How would I do this using the Boost.Lambda functions?

Thanks.

Hi,

Your code has too many syntax errors as is to give advice on how to
modify it. Can you first make it compile and then repost it.

Ivan Novick
http://www.mycppquiz.com

[fgh.vbn.rty]

Ivan Novick wrote:

On Jul 2, 3:27�pm, fgh.vbn....@gma il.com wrote:

I'm having problems setting up the functors to use for_each. Here's an
example:

class A {
public:
� � void getName() { return name; }
private:
� � string name;

};

class B {
public:
� � �vector<intge tIds { return vi; }
� � �A& getA(int idx) { return vA.at(idx); }
� � �void bfunc();
private:
� � �vector<AvA;
� � �vector<intvi ;

}

class C {
public:
� � �void cfunc();
private:
� � �B b;

}

void B::bfunc()
{
� �// populate vi
� �for(int i=0; i<vi.size(); ++i) {
� � � � cout << vA[i].printName() << endl;
� �}

}

void C::cfunc()
{
� �// populate vi
� �vector<intvc = b.getIds();
� �for(int i=0; i<vc.size(); ++i) {
� � � � A& a = getA(vc[i]);
� � � � cout << a.getName() << endl;
� �}

}

Here vA is just a vector of As and vi is a vector of integers that
index into vA. Let's suppose that vA and vi are populated
appropriately. All I'm trying to do is to execute a particular
function on a subset of the As.

I have three questions:
1) How do I replace the for loop in bfunc with a for_each?
2) How do I replace the for loop in cfunc with a for_each?
3) How would I do this using the Boost.Lambda functions?

Thanks.

Hi,

Your code has too many syntax errors as is to give advice on how to
modify it. Can you first make it compile and then repost it.

Ivan Novick
http://www.mycppquiz.com

Sorry, I should've tried it out first. Anyway, the following compiles
without errors on gcc v3.0.4.

#include <iostream>
#include <string>
#include <vector>

using namespace std;

class A {
public:
std::string getName() { return name; }
private:
std::string name;
};

class B {
public:
vector<intgetId s() { return vi; }
A& getA(int idx) { return vA.at(idx); }
void bfunc();
private:
vector<AvA;
vector<intvi;

};

class C {
public:
void cfunc();
private:
B b;
};

void B::bfunc()
{
// populate vA and vi in some fashion
for(int i=0; i<vi.size(); ++i) {
std::cout << vA[i].getName() << std::endl;
}
}

void C::cfunc()
{
// populate vA and vi in some fashion
vector<intvc = b.getIds();
for(int i=0; i<vc.size(); ++i) {
A& a = b.getA(vc[i]);
std::cout << a.getName() << std::endl;
}
}

[Daniel T.]

fg*********@gma il.com wrote:

I'm having problems setting up the functors to use for_each. Here's an
example:

class A {
public:
void getName() { return name; }

error: return-statement with a value, in function returning 'void'

private:
string name;
};

class B {
public:
vector<intgetId s { return vi; }

error: invalid member function declaration

A& getA(int idx) { return vA.at(idx); }
void bfunc();
private:
vector<AvA;
vector<intvi;
}

error: missing semi-colon

class C {
public:
void cfunc();
private:
B b;
}

error: missing semi-colon

void B::bfunc()
{
// populate vi
for(int i=0; i<vi.size(); ++i) {
cout << vA[i].printName() << endl;

error: 'class A' has no member named 'printName'

}
}

void C::cfunc()
{
// populate vi
vector<intvc = b.getIds();
for(int i=0; i<vc.size(); ++i) {
A& a = getA(vc[i]);

error: 'getA' was not declared in this scope

cout << a.getName() << endl;
}
}

Here vA is just a vector of As and vi is a vector of integers that
index into vA.

Frankly, there a so many errors, that I don't think the loops do what
you want them to do, especially bfunc.

Let's suppose that vA and vi are populated
appropriately. All I'm trying to do is to execute a particular
function on a subset of the As.

I have three questions:
1) How do I replace the for loop in bfunc with a for_each?

Don't use for_each, use transform instead:

transform(vA.be gin(), vA.begin() + vi.size(),
ostream_iterato r<string>(cout , "\n"), mem_fun_ref(&A: :getName));

But again, I don't think that's what you want.

2) How do I replace the for loop in cfunc with a for_each?

That function really should be in class B. It pulls B's vi variable out,
and then iterates over B's vA variable. So let's put it there instead:

string B::getNameOf(in t x)
{
return vA.at(x).getNam e();
}

void B::cfunc()
{
transform(vi.be gin(), vi.end(), ostream_iterato r<string>(cout , "\n"),
bind1st(mem_fun (&B::getNameOf) , this));
}

3) How would I do this using the Boost.Lambda functions?

Differently.