### Example: Using boost::bind2nd with boost::mem_fun_ref

Source: https://www.boost.org/doc/libs/latest/libs/functional/index

Demonstrates how to use Boost's binder and member function adapter to apply a member function to elements in a collection. This example highlights the advantage over standard adapters when dealing with member functions taking reference arguments.

```cpp
class Person
{
  public:
    void set_name(const std::string &name);
  // ...
};

std::for_each(c.begin(), c.end(), 
              boost::bind2nd(boost::mem_fun_ref(&Person::set_name), "Fred"));

```

--------------------------------

### Using boost::ptr_fun with std::find_if

Source: https://www.boost.org/doc/libs/latest/libs/functional/ptr_fun

Demonstrates the usage of boost::ptr_fun to adapt a function pointer for use with standard algorithms like std::find_if. This example shows how to find an element in a vector that does not satisfy a given predicate.

```cpp
bool bad(std::string foo) { /* ... */ }
std::vector<std::string> c;
// ...
std::vector<std::string>::iterator it
     = std::find_if(c.begin(), c.end(), std::not1(boost::ptr_fun(bad)));
```

--------------------------------

### Boost.Function enhanced negators with function object traits

Source: https://www.boost.org/doc/libs/latest/libs/functional/ptr_fun

Illustrates the use of Boost's enhanced negators, such as boost::not1, which leverage function object traits for more efficient predicate adaptation with standard algorithms. This example achieves the same result as the previous one but with potentially better performance.

```cpp
std::vector<std::string>::iterator it
     = std::find_if(c.begin(), c.end(), boost::not1(bad));
```

--------------------------------

### Member Function Adapters with Boost (C++)

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Demonstrates using boost::mem_fun to adapt member functions for use with standard algorithms. This example shows retrieving the 'get_name' member function's result from vectors of pointers to Person objects, including const pointers. Requires Boost.Functional.

```cpp
#include <functional>
#define boost std
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>

class Person {
  public:
    Person() {}
    Person(const char *n) : name(n) {}
    const std::string &get_name() const { return name; }
    void print(std::ostream &os) const { os << name << " "; }
    void set_name(const std::string &n) { name = n; std::cout << name << " "; }
    std::string clear_name() { std::string ret = name; name = ""; return ret; }
    void do_something(int) const {}
    bool is_fred() const { return name == "Fred"; }
  private:
    std::string name;
};

namespace {
    bool is_equal(const std::string &s1, const std::string &s2) {
        return s1 == s2;
    }

    bool is_betty(const std::string &s) {
        return s == "Betty";
    }

    void do_set_name(Person *p, const std::string &name) {
        p->set_name(name);
    }
    
    void do_set_name_ref(Person &p, const std::string &name) {
        p.set_name(name);
    }
}

int main() {
    std::vector<Person> v1;
    v1.push_back("Fred");
    v1.push_back("Wilma");
    v1.push_back("Barney");
    v1.push_back("Betty");

    const std::vector<Person> cv1(v1.begin(), v1.end());

    std::vector<std::string> v2;
    v2.push_back("Fred");
    v2.push_back("Wilma");
    v2.push_back("Barney");
    v2.push_back("Betty");

    Person person;
    Person &r = person;

    Person fred("Fred");
    Person wilma("Wilma");
    Person barney("Barney");
    Person betty("Betty");
    std::vector<Person*> v3;
    v3.push_back(&fred);
    v3.push_back(&wilma);
    v3.push_back(&barney);
    v3.push_back(&betty);

    const std::vector<Person*> cv3(v3.begin(), v3.end());
    std::vector<const Person*> v3c(v3.begin(), v3.end());

    std::ostream &os = std::cout;

    // const_mem_fun_t
    std::cout << '\n';
    std::transform(v3.begin(), v3.end(),
                   std::ostream_iterator<std::string>(std::cout, " "),
                   boost::mem_fun(&Person::get_name));

    std::cout << '\n';
    std::transform(cv3.begin(), cv3.end(),
                   std::ostream_iterator<std::string>(std::cout, " "),
                   boost::mem_fun(&Person::get_name));

    std::cout << '\n';
    std::transform(v3c.begin(), v3c.end(),
                   std::ostream_iterator<std::string>(std::cout, " "),

```

--------------------------------

### Using Boost.Functional not1 for std::find_if

Source: https://www.boost.org/doc/libs/latest/libs/functional/negators

Demonstrates how to use Boost.Functional's `not1` adapter with `std::find_if` to find elements that do not satisfy a given predicate. This example shows a common usage pattern for negating a unary function object.

```cpp
bool bad(const Foo &foo) { ... }
std::vector<Foo> c;
...
std::find_if(c.begin(), c.end(), boost::not1(bad));
```

--------------------------------

### Using Boost bind2nd with mem_fun_ref

Source: https://www.boost.org/doc/libs/latest/libs/functional/binders

Demonstrates binding the second argument of a member function reference using Boost binders. This example shows how to use boost::bind2nd with boost::mem_fun_ref to pass std::cout to a member function that takes an std::ostream reference parameter. The Boost implementation avoids compilation errors that would occur with standard library binders.

```cpp
class Foo {
public:
  void bar(std::ostream &);
  // ...
};
// ...
std::vector<Foo> c;
// ...
std::for_each(c.begin(), c.end(), 
              boost::bind2nd(boost::mem_fun_ref(&Foo::bar), std::cout));
```

--------------------------------

### C++ Example of const_mem_fun1_t Issue with std::bind1st

Source: https://www.boost.org/doc/libs/latest/libs/functional/mem_fun

This C++ code demonstrates a scenario where the standard `const_mem_fun1_t` can cause problems. It shows how `std::bind1st` might attempt to initialize a `Foo*` member with a `const Foo*` pointer, leading to a type incompatibility due to the `first_argument_type` mismatch.

```cpp
struct Foo { void bar(int) const; };
const Foo *cp = new Foo;
std::bind1st(std::mem_fun(&Foo::bar), cp);

// This results in:
typedef Foo* first_argument_type;

```

--------------------------------

### Modifying Members with bind1st and mem_fun

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Utilizes boost::bind1st with boost::mem_fun to call a member function that requires a specific object instance and an argument. This example shows setting a name on a person object.

```C++
#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
    // mem_fun1_t, bind1st
    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(boost::mem_fun(&Person::set_name), &person));
#endif
```

--------------------------------

### Pointer to Function Adapters with Boost (C++)

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Demonstrates how to use boost::ptr_fun with boost::not1 and boost::bind1st to adapt pointer-to-function objects for use with standard algorithms. This allows treating free functions as function objects. Requires Boost.Functional.

```cpp
#include <functional>
#define boost std
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>

class Person {
  public:
    Person() {}
    Person(const char *n) : name(n) {}
    const std::string &get_name() const { return name; }
    void print(std::ostream &os) const { os << name << " "; }
    void set_name(const std::string &n) { name = n; std::cout << name << " "; }
    std::string clear_name() { std::string ret = name; name = ""; return ret; }
    void do_something(int) const {}
    bool is_fred() const { return name == "Fred"; }
  private:
    std::string name;
};

namespace {
    bool is_equal(const std::string &s1, const std::string &s2) {
        return s1 == s2;
    }

    bool is_betty(const std::string &s) {
        return s == "Betty";
    }

    void do_set_name(Person *p, const std::string &name) {
        p->set_name(name);
    }
    
    void do_set_name_ref(Person &p, const std::string &name) {
        p.set_name(name);
    }
}

int main() {
    std::vector<Person> v1;
    v1.push_back("Fred");
    v1.push_back("Wilma");
    v1.push_back("Barney");
    v1.push_back("Betty");

    const std::vector<Person> cv1(v1.begin(), v1.end());

    std::vector<std::string> v2;
    v2.push_back("Fred");
    v2.push_back("Wilma");
    v2.push_back("Barney");
    v2.push_back("Betty");

    Person person;
    Person &r = person;

    Person fred("Fred");
    Person wilma("Wilma");
    Person barney("Barney");
    Person betty("Betty");
    std::vector<Person*> v3;
    v3.push_back(&fred);
    v3.push_back(&wilma);
    v3.push_back(&barney);
    v3.push_back(&betty);

    const std::vector<Person*> cv3(v3.begin(), v3.end());
    std::vector<const Person*> v3c(v3.begin(), v3.end());

    std::ostream &os = std::cout;

#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) && !defined(__ICL)
    // pointer_to_unary_function
    std::cout << '\n';
    std::transform(v2.begin(), v2.end(),
                   std::ostream_iterator<bool>(std::cout, " "),
                   boost::not1(boost::ptr_fun(is_betty)));

    // pointer_to_binary_function, bind1st
    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(boost::ptr_fun(do_set_name), &person));

    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(boost::ptr_fun(do_set_name_ref), person));

    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(boost::ptr_fun(do_set_name_ref), r));
#endif
    return 0;
}

```

--------------------------------

### Applying Member Functions with Arguments using bind2nd and mem_fun

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Demonstrates using boost::bind2nd with boost::mem_fun to call a member function that takes an argument. This is often used with algorithms like std::for_each for actions like printing.

```C++
#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
    // const_mem_fun1_t, bind2nd
    std::cout << '\n';
    std::for_each(v3.begin(), v3.end(), boost::bind2nd(boost::mem_fun(&Person::print), std::cout));

    std::cout << '\n';
    std::for_each(v3.begin(), v3.end(), boost::bind2nd(boost::mem_fun(&Person::print), os));
#endif
```

--------------------------------

### Binding Arguments with Boost Functional Adapters (C++)

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Demonstrates using boost::bind1st and boost::bind2nd to fix one argument of a binary function, creating a new function object. This is shown with both free functions and member functions for various use cases. Requires Boost.Functional.

```cpp
#include <functional>
#define boost std
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>

class Person {
  public:
    Person() {}
    Person(const char *n) : name(n) {}
    const std::string &get_name() const { return name; }
    void print(std::ostream &os) const { os << name << " "; }
    void set_name(const std::string &n) { name = n; std::cout << name << " "; }
    std::string clear_name() { std::string ret = name; name = ""; return ret; }
    void do_something(int) const {}
    bool is_fred() const { return name == "Fred"; }
  private:
    std::string name;
};

namespace {
    bool is_equal(const std::string &s1, const std::string &s2) {
        return s1 == s2;
    }

    bool is_betty(const std::string &s) {
        return s == "Betty";
    }

    void do_set_name(Person *p, const std::string &name) {
        p->set_name(name);
    }
    
    void do_set_name_ref(Person &p, const std::string &name) {
        p.set_name(name);
    }
}

int main() {
    std::vector<Person> v1;
    v1.push_back("Fred");
    v1.push_back("Wilma");
    v1.push_back("Barney");
    v1.push_back("Betty");

    const std::vector<Person> cv1(v1.begin(), v1.end());

    std::vector<std::string> v2;
    v2.push_back("Fred");
    v2.push_back("Wilma");
    v2.push_back("Barney");
    v2.push_back("Betty");

    Person person;
    Person &r = person;

    Person fred("Fred");
    Person wilma("Wilma");
    Person barney("Barney");
    Person betty("Betty");
    std::vector<Person*> v3;
    v3.push_back(&fred);
    v3.push_back(&wilma);
    v3.push_back(&barney);
    v3.push_back(&betty);

    const std::vector<Person*> cv3(v3.begin(), v3.end());
    std::vector<const Person*> v3c(v3.begin(), v3.end());

    std::ostream &os = std::cout;

#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) && !defined(__ICL)
    // binary_traits, bind1st, bind2nd
    std::cout << '\n';
    std::transform(v2.begin(), v2.end(),
                   std::ostream_iterator<bool>(std::cout, " "),
                   boost::bind1st(is_equal, "Betty"));

    std::cout << '\n';
    std::transform(v2.begin(), v2.end(),
                   std::ostream_iterator<bool>(std::cout, " "),
                   boost::bind2nd(is_equal, "Betty"));

    // binary_traits
    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(do_set_name, &person));

    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(do_set_name_ref, person));

    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(do_set_name_ref, r));
#endif
    return 0;
}

```

--------------------------------

### Binary Negation with Boost Functional Adapters (C++)

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Illustrates the use of boost::not2 in conjunction with boost::bind1st and boost::bind2nd for binary predicates like is_equal. This allows negating the comparison result when binding arguments to a binary function. Requires Boost.Functional.

```cpp
#include <functional>
#define boost std
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>

class Person {
  public:
    Person() {}
    Person(const char *n) : name(n) {}
    const std::string &get_name() const { return name; }
    void print(std::ostream &os) const { os << name << " "; }
    void set_name(const std::string &n) { name = n; std::cout << name << " "; }
    std::string clear_name() { std::string ret = name; name = ""; return ret; }
    void do_something(int) const {}
    bool is_fred() const { return name == "Fred"; }
  private:
    std::string name;
};

namespace {
    bool is_equal(const std::string &s1, const std::string &s2) {
        return s1 == s2;
    }

    bool is_betty(const std::string &s) {
        return s == "Betty";
    }

    void do_set_name(Person *p, const std::string &name) {
        p->set_name(name);
    }
    
    void do_set_name_ref(Person &p, const std::string &name) {
        p.set_name(name);
    }
}

int main() {
    std::vector<Person> v1;
    v1.push_back("Fred");
    v1.push_back("Wilma");
    v1.push_back("Barney");
    v1.push_back("Betty");

    const std::vector<Person> cv1(v1.begin(), v1.end());

    std::vector<std::string> v2;
    v2.push_back("Fred");
    v2.push_back("Wilma");
    v2.push_back("Barney");
    v2.push_back("Betty");

    Person person;
    Person &r = person;

    Person fred("Fred");
    Person wilma("Wilma");
    Person barney("Barney");
    Person betty("Betty");
    std::vector<Person*> v3;
    v3.push_back(&fred);
    v3.push_back(&wilma);
    v3.push_back(&barney);
    v3.push_back(&betty);

    const std::vector<Person*> cv3(v3.begin(), v3.end());
    std::vector<const Person*> v3c(v3.begin(), v3.end());

    std::ostream &os = std::cout;

#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) && !defined(__ICL)
    // binary_traits, binary_negate
    std::cout << '\n';
    std::transform(v2.begin(), v2.end(),
                   std::ostream_iterator<bool>(std::cout, " "),
                   boost::bind1st(boost::not2(is_equal), "Betty"));

    std::cout << '\n';
    std::transform(v2.begin(), v2.end(),
                   std::ostream_iterator<bool>(std::cout, " "),
                   boost::bind2nd(boost::not2(is_equal), "Betty"));
#endif
    return 0;
}

```

--------------------------------

### Unary Negation with Boost Functional Adapters (C++)

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Demonstrates using boost::not1 with a predicate function (is_betty) and a member function (Person::is_fred) to transform collections. It applies the negation to the result of the predicate. Requires Boost.Functional.

```cpp
#include <functional>
#define boost std
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
#include <vector>

class Person {
  public:
    Person() {}
    Person(const char *n) : name(n) {}
    const std::string &get_name() const { return name; }
    void print(std::ostream &os) const { os << name << " "; }
    void set_name(const std::string &n) { name = n; std::cout << name << " "; }
    std::string clear_name() { std::string ret = name; name = ""; return ret; }
    void do_something(int) const {}
    bool is_fred() const { return name == "Fred"; }
  private:
    std::string name;
};

namespace {
    bool is_equal(const std::string &s1, const std::string &s2) {
        return s1 == s2;
    }

    bool is_betty(const std::string &s) {
        return s == "Betty";
    }

    void do_set_name(Person *p, const std::string &name) {
        p->set_name(name);
    }
    
    void do_set_name_ref(Person &p, const std::string &name) {
        p.set_name(name);
    }
}

int main() {
    std::vector<Person> v1;
    v1.push_back("Fred");
    v1.push_back("Wilma");
    v1.push_back("Barney");
    v1.push_back("Betty");

    const std::vector<Person> cv1(v1.begin(), v1.end());

    std::vector<std::string> v2;
    v2.push_back("Fred");
    v2.push_back("Wilma");
    v2.push_back("Barney");
    v2.push_back("Betty");

    Person person;
    Person &r = person;

    Person fred("Fred");
    Person wilma("Wilma");
    Person barney("Barney");
    Person betty("Betty");
    std::vector<Person*> v3;
    v3.push_back(&fred);
    v3.push_back(&wilma);
    v3.push_back(&barney);
    v3.push_back(&betty);

    const std::vector<Person*> cv3(v3.begin(), v3.end());
    std::vector<const Person*> v3c(v3.begin(), v3.end());

    std::ostream &os = std::cout;

#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) && !defined(__ICL)
    // unary_traits, unary_negate
    std::transform(v2.begin(), v2.end(),
                   std::ostream_iterator<bool>(std::cout, " "),
                   boost::not1(is_betty));

    std::cout << '\n';
    std::transform(v1.begin(), v1.end(),
                   std::ostream_iterator<bool>(std::cout, " "),
                   boost::not1(boost::mem_fun_ref(&Person::is_fred)));
#endif
    return 0;
}

```

--------------------------------

### Standard C++ pointer_to_unary_function declaration

Source: https://www.boost.org/doc/libs/latest/libs/functional/ptr_fun

Shows the standard C++ declaration for the pointer_to_unary_function template. It defines how a function pointer is wrapped and how its operator() is invoked, highlighting potential performance issues with value type arguments.

```cpp
template <class Arg, class Result>
class pointer_to_unary_function : public unary_function<Arg, Result> {
public:
  explicit pointer_to_unary_function(Result (* f)(**Arg**));
  Result operator()(**Arg** x) const;
};
```

--------------------------------

### Boost.Function operator() using call_traits for optimized argument passing

Source: https://www.boost.org/doc/libs/latest/libs/functional/ptr_fun

Presents the optimized declaration of operator() within Boost.Function, utilizing the call_traits<Arg>::param_type typedef. This approach dynamically determines the optimal way to pass arguments (by value or const reference) based on the argument type, improving efficiency and avoiding issues like references to references.

```cpp
Result operator()(typename call_traits<Arg>::param_type x) const
```

--------------------------------

### C++ Boost.Function mem_fun1_t with call_traits

Source: https://www.boost.org/doc/libs/latest/libs/functional/mem_fun

This C++ code demonstrates how Boost.Function improves `mem_fun1_t` by using `call_traits<A>::param_type` for the second argument of `operator()`. This approach optimizes argument passing, avoiding unnecessary copies for value types and preventing issues with reference types.

```cpp
S operator()(T* p, typename call_traits<A>::param_type x) const

```

--------------------------------

### C++ Standard Library mem_fun1_t Argument Handling

Source: https://www.boost.org/doc/libs/latest/libs/functional/mem_fun

This C++ code snippet illustrates the definition of `mem_fun1_t` from the C++ Standard Library. It points out that the second argument to `operator()` is passed by value, which can lead to inefficiencies due to multiple copies for non-reference types.

```cpp
template <class S, class T, class A> class mem_fun1_t
  : public binary_function<T*, A, S> {
public:
  explicit mem_fun1_t(S (T::*p)(A));
  S operator()(T* p, A x) const;
};

```

--------------------------------

### Boost binder2nd constructor using call_traits

Source: https://www.boost.org/doc/libs/latest/libs/functional/binders

Demonstrates how Boost's enhanced binder2nd avoids the references to references problem by using call_traits templates. The constructor parameter type is determined by call_traits, which properly handles reference types and prevents illegal reference to reference formations.

```cpp
binder2nd(const Operation& x,
          typename call_traits<
             typename binary_traits<Operation>::second_argument_type
          >::param_type y)
```

--------------------------------

### Standard binder2nd template definition with reference issue

Source: https://www.boost.org/doc/libs/latest/libs/functional/binders

Shows the standard C++ library binder2nd template class definition that creates the references to references problem. When the second_argument_type is a reference (e.g., std::ostream&), the constructor parameter y becomes a reference to a reference (std::ostream&&), which is illegal in C++.

```cpp
template <class Operation>
class binder2nd
    : public unary_function<typename Operation::first_argument_type,
                            typename Operation::result_type> {
...
public:
  binder2nd(const Operation& x,
            const typename Operation::second_argument_type& y);
  ...
};
```

--------------------------------

### Calling Member Functions with mem_fun and std::transform

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Applies a member function to each element in a range using std::transform and boost::mem_fun. This is useful for operations that return a value, such as getters.

```C++
std::cout << '\n';
    std::transform(v1.begin(), v1.end(),
                   std::ostream_iterator<std::string>(std::cout, " "),
                   boost::mem_fun(&Person::get_name));
```

--------------------------------

### Boost.Functional unary_negate class template definition

Source: https://www.boost.org/doc/libs/latest/libs/functional/negators

Illustrates the C++ Standard Library's definition of the `unary_negate` class template. This serves as a baseline for understanding the improvements provided by Boost.Functional's version, particularly regarding argument type handling.

```cpp
template <class Predicate>
  class unary_negate
    : public unary_function<typename Predicate::argument_type,bool> {
public:
  explicit unary_negate(const Predicate& pred);
  bool operator()(const typename Predicate::argument_type& x) const;
};
```

--------------------------------

### Applying Const Member Functions with Arguments using bind2nd and mem_fun_ref

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Combines boost::bind2nd and boost::mem_fun_ref to invoke const member functions that require arguments on elements within a range. Suitable for operations on const objects or references.

```C++
#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
    // const_mem_fun1_ref_t, bind2nd
    std::cout << '\n';
    std::for_each(v1.begin(), v1.end(), boost::bind2nd(boost::mem_fun_ref(&Person::print), std::cout));

    std::cout << '\n';
    std::for_each(v1.begin(), v1.end(), boost::bind2nd(boost::mem_fun_ref(&Person::print), os));
#endif
```

--------------------------------

### C++ Standard Library const_mem_fun1_t Definition

Source: https://www.boost.org/doc/libs/latest/libs/functional/mem_fun

This C++ code snippet shows the definition of `const_mem_fun1_t` as specified in the C++ Standard Library. It highlights a potential issue with the `first_argument_type` typedef, which can lead to type mismatches when used with functions like `std::bind1st`.

```cpp
template <class S, class T, class A> class const_mem_fun1_t
  : public binary_function<T*, A, S> {
public:
  explicit const_mem_fun1_t(S (T::*p)(A) const);
  S operator()(const T* p, A x) const;
};

```

--------------------------------

### Modifying Members with bind1st and mem_fun_ref

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Employs boost::bind1st with boost::mem_fun_ref to modify members of objects using a reference and an argument. This allows for in-place modification of object state.

```C++
#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
    // mem_fun1_ref_t, bind1st
    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(boost::mem_fun_ref(&Person::set_name), person));

    std::cout << '\n';
    std::for_each(v2.begin(), v2.end(), boost::bind1st(boost::mem_fun_ref(&Person::set_name), r));
#endif
```

--------------------------------

### Define binary_traits template with type members

Source: https://www.boost.org/doc/libs/latest/libs/functional/function_traits

The binary_traits template struct extracts type information from binary functions or function objects. It provides function_type, param_type, result_type, first_argument_type, and second_argument_type. This template is used for adapters that work with binary operations and allows uniform handling of plain functions and adaptable function objects.

```C++
template <typename T>
struct binary_traits {
  typedef T function_type;
  typedef typename T::param_type param_type;
  typedef typename T::result_type result_type;
  typedef typename T::first_argument_type first_argument_type;
  typedef typename T::second_argument_type second_argument_type;
};
```

--------------------------------

### Use unary_traits in function object adapter constructor

Source: https://www.boost.org/doc/libs/latest/libs/functional/function_traits

Demonstrates using unary_traits::param_type in a constructor to optimally pass a function or function object as a parameter. Function objects are passed by const reference while function pointers are passed by value, providing efficient parameter passing regardless of the predicate type.

```C++
template <class Predicate>
class unary_negate {
public:
  explicit unary_negate(typename unary_traits<Predicate>::param_type x)
    : pred(x)
  {}
private:
  typename unary_traits<Predicate>::function_type pred;
};
```

--------------------------------

### Boost.Functional unary_negate operator() with call_traits

Source: https://www.boost.org/doc/libs/latest/libs/functional/negators

Shows how Boost.Functional's `unary_negate` can declare its `operator()` argument using `call_traits<...>::param_type`. This approach efficiently handles both reference and value types for the predicate's argument, avoiding unnecessary copies and potential reference-to-reference issues.

```cpp
bool operator()(typename call_traits<typename Predicate::argument_type>::param_type x) const
```

--------------------------------

### Clearing Member Data with mem_fun and std::transform

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Applies a member function, such as 'clear_name', to each element in a range using std::transform and boost::mem_fun. This is useful for resetting or clearing data within objects.

```C++
// mem_fun_t
    std::cout << '\n';
    std::transform(v3.begin(), v3.end(), std::ostream_iterator<std::string>(std::cout, " "),
                   boost::mem_fun(&Person::clear_name));
```

--------------------------------

### Calling Const Member Functions with mem_fun_ref and std::transform

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Uses std::transform with boost::mem_fun_ref to apply a const member function to elements in a range. This is suitable for accessing data from const objects or const references.

```C++
std::cout << '\n';
    std::transform(cv1.begin(), cv1.end(),
                   std::ostream_iterator<std::string>(std::cout, " "),
                   boost::mem_fun_ref(&Person::get_name));
```

--------------------------------

### Define unary_traits template with type members

Source: https://www.boost.org/doc/libs/latest/libs/functional/function_traits

The unary_traits template struct extracts type information from unary functions or function objects. It provides function_type (the function/object type itself), param_type (optimal parameter passing type), result_type (return type), and argument_type (parameter type). Used for declaring function objects in adapters and enabling uniform treatment of functions and function objects.

```C++
template <typename T>
struct unary_traits {
  typedef T function_type;
  typedef typename T::param_type param_type;
  typedef typename T::result_type result_type;
  typedef typename T::argument_type argument_type;
};
```

--------------------------------

### Clearing Member Data with mem_fun_ref and std::transform

Source: https://www.boost.org/doc/libs/latest/libs/functional/test/function_test

Uses std::transform with boost::mem_fun_ref to apply a member function for clearing data to elements in a range. This is efficient for modifying object state directly via references.

```C++
// mem_fun_ref_t
    std::cout << '\n';
    std::transform(v1.begin(), v1.end(), std::ostream_iterator<std::string>(std::cout, " "),
                   boost::mem_fun_ref(&Person::clear_name));
```

--------------------------------

### Replace standard traits with boost unary_traits

Source: https://www.boost.org/doc/libs/latest/libs/functional/function_traits

Shows how to use boost::unary_traits to extract argument types from a predicate template parameter instead of directly accessing Operation::argument_type. This approach works uniformly with both plain functions and adaptable function objects, eliminating the need for ptr_fun in most cases.

```C++
typename boost::unary_traits<Operation>::argument_type
```

--------------------------------

### Use unary_traits in function object adapter declaration

Source: https://www.boost.org/doc/libs/latest/libs/functional/function_traits

Demonstrates using unary_traits::function_type to declare a predicate member in a template class that can accept both function pointers and adaptable function objects. The function_type typedef allows proper instantiation of template classes with function types, which would otherwise be impossible due to C++ template specialization rules.

```C++
template <class Predicate>
class unary_negate {
private:
  typename unary_traits<Predicate>::function_type pred;
};
```

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