Code needs a lot of help, but the biggest problems are;

1) for_each expects a function object that takes one param, while
makefile::operator() expects 2 params. No matching func...

2) Your definition of makefile::operator() does not call
makefile::apply() at all. operator() is empty. You seem to
misunderstand
function objects. In your code, makefile::apply() never gets called.

3) you don't have an instance of makefile class. You need to
instantiate and
get an object. Something like;

makefile my_obj;
for_each(lString.begin(), lString.end(), my_obj);

(Note that it's my_obj, not my_obj() above...)

for_each will call my_obj() which would execute operator() in your
makefile class.

Hope this helps,

Tolga Ceylan

learning schrieb:

I am trying to learn STL but got stuck in for_each().
What I intend to do in the following is to make a list with each
element as a string.
add the string elements to the list until it has 10 elements. each
element is the same 1234567890. then I want to use for_each to iterate
the list, and for each to call apply() whihc is create a filen with
name the same as string al; and within each file, it contains the
content of the list element.
I go stuck in making apply to work. Can anyone help?? the following is
the code, it compiles under vc++ 8.

It doesn't compile.

Thanks


#include <algorithm>
#include <list>
#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>

using namespace std;

class makefile{

public:
void operator()(std::string sth, std::string sth2){

};
void apply(std::string s, std::string name){

Put this code in operator().

for_each supplies only one argument, so it should be:

void operator()(std::string name) // or:
void operator()(const std::string& name)

std::filebuf buffer;
std::ostream output(&buffer);
buffer.open(name.c_str(), std::ios::out);
output << s << std::endl;

Why don't you use a simple ofstream object?

std::ofstream output(name.c_str());
output << s << std::endl;

}
};

int main(){
std::string s("1234567890");
std::string al("abc");
list<std::string> lString;
for (int i=0; i <= 9; i++) {
//std::string tmp(itoa(i));
al = s+ s.at(i);

What is 'al' for?

lString.push_back(s);
}
//for_each();

for_each(lString.begin(),lString.end(),apply());

for_each(lString.begin(), lString.end(), makefile());

return 0;
}

Your makefile() functor opens a file with name given to it and outputs a
string given as second argument. for_each can only work with one element at
a time.
If you want multiple files with different output strings, try a
std::list< std::pair<std::string, std::string> >
with first string being the filename and second string the text to output.

The functor would be like this:

struct makefile
{
void operator()(const std::pair<std::string, std::string>& record) const
{
std::ofstream file(record.first.c_str());
file << record.second << std::endl;
}
}

--
Thomas