generate

[Chameleon]

I totally messed up with this:

We have
--------------------------------------
generate(v.begin(), v.end(), my_func);
--------------------------------------

and my_func:
-----------
int my_func();
-----------

So, if my_func() does not take parameters, how can generate data?
I see in examples, it uses static variables, but it isn't thread-safe.

I have a class, and I want from data of class produce values to fill
vector v. But in my case my_func() MUST NOT be static. How can I pass a
non-static member function to generate()?

------------------------------------------------
template<class ForwardIterator, class Generator>
void generate(
ForwardIterator _First,
ForwardIterator _Last,
Generator _Gen
);
------------------------------------------------
What is "class Generator"?
Is something like "Interface" in Java?
I must implement a specific method in my class, and my class must derive
from Generator?

thanks and sorry for my bombing (3 questions in a day)

[Alf P. Steinbach]

* Chameleon:

I totally messed up with this:

We have
--------------------------------------
generate(v.begin(), v.end(), my_func);
--------------------------------------

and my_func:
-----------
int my_func();
-----------

So, if my_func() does not take parameters, how can generate data?
I see in examples, it uses static variables, but it isn't thread-safe.

I have a class, and I want from data of class produce values to fill
vector v. But in my case my_func() MUST NOT be static. How can I pass a
non-static member function to generate()?

I'd recommend using a simple loop instead of std::generate.

But if you feel you absolutely must use std::generate, pass it a functor
object.

That's an object that provides an operator(); see the FAQ for more
information.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Ron Natalie]

Chameleon wrote:

What is "class Generator"?
Is something like "Interface" in Java?
I must implement a specific method in my class, and my class must derive
from Generator?

First off, in a template definition, the word "class" in the argument
just means any type (doesn't necessarily have to be a class).

The function class in the template, doesn't have to be a function.
It can be a object of a class that implements operator(). That
object can keep track in it's own member variables.

[Victor Bazarov]

Chameleon wrote:

I totally messed up with this:

We have
--------------------------------------
generate(v.begin(), v.end(), my_func);
--------------------------------------

and my_func:
-----------
int my_func();
-----------

So, if my_func() does not take parameters, how can generate data?
It could be just 'rand', right?
I see in examples, it uses static variables, but it isn't thread-safe.
No, I suppose not. Threads are not part of the language, though.
I have a class, and I want from data of class produce values to fill
vector v. But in my case my_func() MUST NOT be static. How can I pass a
non-static member function to generate()?
You don't pass a member. You pass an object of your class.
------------------------------------------------
template<class ForwardIterator, class Generator>
void generate(
ForwardIterator _First,
ForwardIterator _Last,
Generator _Gen
);
------------------------------------------------
What is "class Generator"?
A functor.
Is something like "Interface" in Java?
No. The whole idea is that it should have data members.
I must implement a specific method in my class, and my class must derive
from Generator?
Yes, you need to implement a function call operator.
thanks and sorry for my bombing (3 questions in a day)

Don't be sorry, the more you ask, the more you learn (hopefully).

BTW, what book on the Standard library are you currently reading that does
not answer those concerns/questions?

V
--
Please remove capital As from my address when replying by mail

[Chameleon]

Victor Bazarov wrote:

Chameleon wrote:

I totally messed up with this:

We have
--------------------------------------
generate(v.begin(), v.end(), my_func);
--------------------------------------

and my_func:
-----------
int my_func();
-----------

So, if my_func() does not take parameters, how can generate data?

It could be just 'rand', right?

I see in examples, it uses static variables, but it isn't thread-safe.

No, I suppose not. Threads are not part of the language, though.

I have a class, and I want from data of class produce values to fill
vector v. But in my case my_func() MUST NOT be static. How can I pass
a non-static member function to generate()?

You don't pass a member. You pass an object of your class.

------------------------------------------------
template<class ForwardIterator, class Generator>
void generate(
ForwardIterator _First,
ForwardIterator _Last,
Generator _Gen
);
------------------------------------------------
What is "class Generator"?

A functor.

Is something like "Interface" in Java?

No. The whole idea is that it should have data members.

I must implement a specific method in my class, and my class must
derive from Generator?

Yes, you need to implement a function call operator.

thanks and sorry for my bombing (3 questions in a day)

Don't be sorry, the more you ask, the more you learn (hopefully).

BTW, what book on the Standard library are you currently reading that does
not answer those concerns/questions?

I read Thinking in C++ but about 4 years before and until now, I used
C++ like a C with classes, (multiple) inheritance, string, vector, map
and other goodies. For instance I NEVER used iterators before. Only to
have access in algorithm members like:
sort(v.begin() + index_start, v.begin() + index_end);

[Victor Bazarov]

Chameleon wrote:

[..]
I read Thinking in C++ but about 4 years before and until now, I used
C++ like a C with classes, (multiple) inheritance, string, vector, map
and other goodies. For instance I NEVER used iterators before. Only to
have access in algorithm members like:
sort(v.begin() + index_start, v.begin() + index_end);

Well, that's a good start. Now you need to add your own predicate.
Both a function and a class. Should make you learn a tad.

With all due respect to Bruce Eckel, you need to get yourself a copy
on the Standard Library (Josuttis is the best) and I also recommend
"C++ Templates" by Vandevoorde and Josuttis.

V
--
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