test/bll_compatibility/bind_tests_advanced.cpp

//  bind_tests_advanced.cpp  -- The Boost Lambda Library ------------------
//
// Copyright (C) 2000-2003 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
// Copyright (C) 2000-2003 Gary Powell (powellg@amazon.com)
// Copyright (C) 2010 Steven Watanabe
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// For more information, see www.boost.org

// -----------------------------------------------------------------------


#include <boost/core/lightweight_test.hpp>

/*
#include "boost/lambda/lambda.hpp"
#include "boost/lambda/bind.hpp"
*/
#include <boost/phoenix/core.hpp>
#include <boost/phoenix/operator.hpp>
#include <boost/phoenix/bind.hpp>
#include <boost/phoenix/scope.hpp>

#include "boost/any.hpp"
#include "boost/type_traits/is_reference.hpp"
#include "boost/mpl/assert.hpp"
#include "boost/mpl/if.hpp"

#include <iostream>

#include <functional>

#include <algorithm>

namespace phoenix = boost::phoenix;

int sum_0() { return 0; }
int sum_1(int a) { return a; }
int sum_2(int a, int b) { return a+b; }

int product_2(int a, int b) { return a*b; }

// unary function that returns a pointer to a binary function
typedef int (*fptr_type)(int, int);
fptr_type sum_or_product(bool x) {
  return x ? sum_2 : product_2;
}

// a nullary functor that returns a pointer to a unary function that
// returns a pointer to a binary function.
struct which_one {
  typedef fptr_type (*result_type)(bool x);

  // Was:
  // template <class T> struct sig { typedef result_type type; };
  // phoenix follows the standard result_of protocol

  result_type operator()() const { return sum_or_product; }
};

void test_nested_binds()
{
    using phoenix::bind;
    using phoenix::placeholders::_1;
    using phoenix::placeholders::_2;
    using phoenix::placeholders::_3;
  int j = 2; int k = 3;

// bind calls can be nested (the target function can be a lambda functor)
// The interpretation is, that the innermost lambda functor returns something
// that is bindable (another lambda functor, function pointer ...)
  bool condition;

  condition = true;
  BOOST_TEST_EQ(bind(bind(&sum_or_product, _1), 1, 2)(condition), 3);
  BOOST_TEST_EQ(bind(bind(&sum_or_product, _1), _2, _3)(condition, j, k), 5);

  condition = false;
  BOOST_TEST_EQ(bind(bind(&sum_or_product, _1), 1, 2)(condition), 2);
  BOOST_TEST_EQ(bind(bind(&sum_or_product, _1), _2, _3)(condition, j, k), 6);


  which_one wo;
  BOOST_TEST_EQ(bind(bind(bind(wo), _1), _2, _3)(condition, j, k), 6);


  return;
}


// unlambda -------------------------------------------------

  // Sometimes it may be necessary to prevent the argument substitution of
  // taking place. For example, we may end up with a nested bind expression
  // inadvertently when using the target function is received as a parameter

template<class F>
int call_with_100(const F& f) {


  //  bind(f, _1)(make_const(100));
  // This would result in;
  // bind(_1 + 1, _1)(make_const(100)) , which would be a compile time error

  //return bl::bind(unlambda(f), _1)(make_const(100));
  return 5;

  // for other functors than lambda functors, unlambda has no effect
  // (except for making them const)
}

template<class F>
int call_with_101(const F& f) {

  //return bind(unlambda(f), _1)(make_const(101));
  return 5;

}


void test_unlambda() {

    using phoenix::placeholders::_1;
    using phoenix::placeholders::_2;

  int i = 1;

  //BOOST_TEST_EQ(unlambda(_1 + _2)(i, i), 2);
  //BOOST_TEST_EQ(unlambda(++var(i))(), 2);
  //BOOST_TEST_EQ(call_with_100(_1 + 1), 101);


  //BOOST_TEST_EQ(call_with_101(_1 + 1), 102);

  //BOOST_TEST_EQ(call_with_100(bl::bind(std_functor(std::bind1st(std::plus<int>(), 1)), _1)), 101);

  // Was:
  // std_functor insturcts LL that the functor defines a result_type typedef
  // rather than a sig template.
  //bl::bind(std_functor(std::plus<int>()), _1, _2)(i, i);
  // Standard functors can be used without any further action needed.
  phoenix::bind(std::plus<int>(), _1, _2)(i, i);
}


// protect ------------------------------------------------------------

// protect protects a lambda functor from argument substitution.
// protect is useful e.g. with nested stl algorithm calls.

#if 0
namespace ll {

struct for_each {

  // Was:
  // note, std::for_each returns it's last argument
  // We want the same behaviour from our ll::for_each.
  // However, the functor can be called with any arguments, and
  // the return type thus depends on the argument types.

  // 1. Provide a sig class member template:

  // The return type deduction system instantiate this class as:
  // sig<Args>::type, where Args is a boost::tuples::cons-list
  // The head type is the function object type itself
  // cv-qualified (so it is possilbe to provide different return types
  // for differently cv-qualified operator()'s.

  // The tail type is the list of the types of the actual arguments the
  // function was called with.
  // So sig should contain a typedef type, which defines a mapping from
  // the operator() arguments to its return type.
  // Note, that it is possible to provide different sigs for the same functor
  // if the functor has several operator()'s, even if they have different
  // number of arguments.

  // Note, that the argument types in Args are guaranteed to be non-reference
  // types, but they can have cv-qualifiers.

  //  template <class Args>
  //struct sig {
  //  typedef typename boost::remove_const<
  //        typename boost::tuples::element<3, Args>::type
  //     >::type type;
  //};

  // We follow the result_of protocol ...
  template <typename Sig>
  struct result;

  template <typename This, typename A, typename B, typename C>
  struct result<This(A&,B&,C&)>
  {typedef C type;};

  template <class A, class B, class C>
  C
  operator()(const A& a, const B& b, const C& c) const
  { return std::for_each(a, b, c);}
};

} // end of ll namespace
#endif

void test_protect()
{
    using phoenix::placeholders::_1;
  int i = 0;
  int b[3][5];
  int* a[3];

  for(int j=0; j<3; ++j) a[j] = b[j];

  // Was:
  //std::for_each(a, a+3,
  //         bind(ll::for_each(), _1, _1 + 5, protect(_1 = ++var(i))));
#if 0
  std::for_each(a, a+3,
           phoenix::bind(ll::for_each(), _1, _1 + 5, phoenix::lambda[_1 = ++phoenix::ref(i)]));
#endif


  // This is how you could output the values (it is uncommented, no output
  // from a regression test file):
  //  std::for_each(a, a+3,
  //                bind(ll::for_each(), _1, _1 + 5,
  //                     std::cout << constant("\nLine ") << (&_1 - a) << " : "
  //                     << protect(_1)
  //                     )
  //               );

  int sum = 0;

  // Was:
  //std::for_each(a, a+3,
  //         bind(ll::for_each(), _1, _1 + 5,
  //              protect(sum += _1))
  //             );
#if 0
  std::for_each(a, a+3,
           phoenix::bind(ll::for_each(), _1, _1 + 5,
                phoenix::lambda[phoenix::ref(sum) += _1])
               );
  BOOST_TEST_EQ(sum, (1+15)*15/2);
#endif

  sum = 0;

  // Was:
  //std::for_each(a, a+3,
  //         bind(ll::for_each(), _1, _1 + 5,
  //              sum += 1 + protect(_1)) // add element count
  //             );
#if 0
  std::for_each(a, a+3,
           phoenix::bind(ll::for_each(), _1, _1 + 5,
                phoenix::ref(sum) += 1 + phoenix::lambda[_1]) // add element count
               );
  BOOST_TEST_EQ(sum, (1+15)*15/2 + 15);
#endif

  // Was:
  //(1 + protect(_1))(sum);
  (1 + phoenix::lambda[_1])(sum);

  int k = 0;
  // Was:
  //((k += constant(1)) += protect(constant(2)))();
  ((phoenix::ref(k) += 1) += phoenix::lambda[phoenix::cref(2)])();
  BOOST_TEST_EQ(k, 1);

  k = 0;
  // Was:
  //((k += constant(1)) += protect(constant(2)))()();
  //((phoenix::ref(k) += 1) += phoenix::lambda[std::cout << phoenix::cref("ok ...\n"), phoenix::cref(2)])()();
  //std::cout << ((phoenix::ref(k) += 1) + phoenix::lambda[phoenix::cref(2)])()() << "\n";
  ((phoenix::ref(k) += 1) += 2)();
  std::cout << k << "\n";
  BOOST_TEST_EQ(k, 3);

  // note, the following doesn't work:

  //  ((var(k) = constant(1)) = protect(constant(2)))();

  // (var(k) = constant(1))() returns int& and thus the
  // second assignment fails.

  // We should have something like:
  // bind(var, var(k) = constant(1)) = protect(constant(2)))();
  // But currently var is not bindable.

  // The same goes with ret. A bindable ret could be handy sometimes as well
  // (protect(std::cout << _1), std::cout << _1)(i)(j); does not work
  // because the comma operator tries to store the result of the evaluation
  // of std::cout << _1 as a copy (and you can't copy std::ostream).
  // something like this:
  // (protect(std::cout << _1), bind(ref, std::cout << _1))(i)(j);


  // the stuff below works, but we do not want extra output to
  // cout, must be changed to stringstreams but stringstreams do not
  // work due to a bug in the type deduction. Will be fixed...
#if 0
  // But for now, ref is not bindable. There are other ways around this:

    int x = 1, y = 2;
    (protect(std::cout << _1), (std::cout << _1, 0))(x)(y);

  // added one dummy value to make the argument to comma an int
  // instead of ostream&

  // Note, the same problem is more apparent without protect
  //   (std::cout << 1, std::cout << constant(2))(); // does not work

    (boost::ref(std::cout << 1), std::cout << constant(2))(); // this does

#endif

}


void test_lambda_functors_as_arguments_to_lambda_functors() {
    using phoenix::bind;
    using phoenix::cref;
    using phoenix::placeholders::_1;
    using phoenix::placeholders::_2;
    using phoenix::placeholders::_3;

// lambda functor is a function object, and can therefore be used
// as an argument to another lambda functors function call object.

  // Note however, that the argument/type substitution is not entered again.
  // This means, that something like this will not work:

    (_1 + _2)(_1, cref(7));
    (_1 + _2)(bind(&sum_0), cref(7));

    // or it does work, but the effect is not to call
    // sum_0() + 7, but rather
    // bind(sum_0) + 7, which results in another lambda functor
    // (lambda functor + int) and can be called again
  BOOST_TEST_EQ((_1 + _2)(bind(&sum_0), cref(7))(), 7);

  int i = 3, j = 12;
  BOOST_TEST_EQ((_1 - _2)(_2, _1)(i, j), j - i);

  // also, note that lambda functor are no special case for bind if received
  // as a parameter. In oder to be bindable, the functor must
  // defint the sig template, or then
  // the return type must be defined within the bind call. Lambda functors
  // do define the sig template, so if the return type deduction system
  // covers the case, there is no need to specify the return type
  // explicitly.

  int a = 5, b = 6;

  // Let type deduction find out the return type
  //BOOST_TEST_EQ(bind(_1, _2, _3)(unlambda(_1 + _2), a, b), 11);

  //specify it yourself:
  BOOST_TEST_EQ(bind(_1, _2, _3)(_1 + _2, a, b), 11);

  bind(_1,1.0)(_1+_1);
  return;

}
/*
template<class T>
struct func {
  template<class Args>
  struct sig {
    typedef typename boost::tuples::element<1, Args>::type arg1;
    // If the argument type is not the same as the expected type,
    // return void, which will cause an error.  Note that we
    // can't just assert that the types are the same, because
    // both const and non-const versions can be instantiated
    // even though only one is ultimately used.
    typedef typename boost::mpl::if_<boost::is_same<arg1, T>,
      typename boost::remove_const<arg1>::type,
      void
    >::type type;
  };
  template<class U>
  U operator()(const U& arg) const {
    return arg;
  }
};

void test_sig()
{
  int i = 1;
  BOOST_TEST_EQ(bind(func<int>(), 1)(), 1);
  BOOST_TEST_EQ(bind(func<const int>(), _1)(static_cast<const int&>(i)), 1);
  BOOST_TEST_EQ(bind(func<int>(), _1)(i), 1);
}

class base {
public:
  virtual int foo() = 0;
};

class derived : public base {
public:
  virtual int foo() {
    return 1;
  }
};

void test_abstract()
{
  derived d;
  base& b = d;
  BOOST_TEST_EQ(bind(&base::foo, var(b))(), 1);
  BOOST_TEST_EQ(bind(&base::foo, *_1)(&b), 1);
}
*/

int main()
{
  test_nested_binds();
  test_unlambda();
  test_protect();
  test_lambda_functors_as_arguments_to_lambda_functors();
  //test_sig();
  //test_abstract();
  return boost::report_errors();
}