///////////////////////////////////////////////////////////////////////////////
// examples.hpp
//
// Copyright 2008 Eric Niebler. 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)
#include <iostream>
#include <boost/config.hpp>
#include <boost/mpl/min_max.hpp>
#include <boost/proto/core.hpp>
#include <boost/proto/transform.hpp>
#include <boost/proto/functional/fusion.hpp>
#include <boost/utility/result_of.hpp>
#include <boost/fusion/include/cons.hpp>
#include <boost/fusion/include/tuple.hpp>
#include <boost/fusion/include/pop_front.hpp>
#include <boost/test/unit_test.hpp>
namespace mpl = boost::mpl;
namespace proto = boost::proto;
namespace fusion = boost::fusion;
using proto::_;
template<int I>
struct placeholder
{};
namespace test1
{
//[ CalcGrammar
// This is the grammar for calculator expressions,
// to which we will attach transforms for computing
// the expressions' arity.
/*<< A Calculator expression is ... >>*/
struct CalcArity
: proto::or_<
/*<< _1, or ... >>*/
proto::terminal< placeholder<0> >
/*<< _2, or ... >>*/
, proto::terminal< placeholder<1> >
/*<< some other terminal, or ... >>*/
, proto::terminal< _ >
/*<< a unary expression where the operand is a calculator expression, or ... >>*/
, proto::unary_expr< _, CalcArity >
/*<< a binary expression where the operands are calculator expressions >>*/
, proto::binary_expr< _, CalcArity, CalcArity >
>
{};
//]
}
//[ binary_arity
/*<< The `CalculatorArity` is a transform for calculating
the arity of a calculator expression. It will be define in
terms of `binary_arity`, which is defined in terms of
`CalculatorArity`; hence, the definition is recursive.>>*/
struct CalculatorArity;
// A custom transform that returns the arity of a unary
// calculator expression by finding the arity of the
// child expression.
struct unary_arity
/*<< Custom transforms should inherit from
transform<>. In some cases, (e.g., when the transform
is a template), it is also necessary to specialize
the proto::is_callable<> trait. >>*/
: proto::transform<unary_arity>
{
template<typename Expr, typename State, typename Data>
/*<< Transforms have a nested `impl<>` that is
a valid TR1 function object. >>*/
struct impl
: proto::transform_impl<Expr, State, Data>
{
/*<< Get the child. >>*/
typedef typename proto::result_of::child<Expr>::type child_expr;
/*<< Apply `CalculatorArity` to find the arity of the child. >>*/
typedef typename boost::result_of<CalculatorArity(child_expr, State, Data)>::type result_type;
/*<< The `unary_arity` transform doesn't have an interesting
runtime counterpart, so just return a default-constructed object
of the correct type. >>*/
result_type operator ()(proto::ignore, proto::ignore, proto::ignore) const
{
return result_type();
}
};
};
// A custom transform that returns the arity of a binary
// calculator expression by finding the maximum of the
// arities of the mpl::int_<2> child expressions.
struct binary_arity
/*<< All custom transforms should inherit from
transform. In some cases, (e.g., when the transform
is a template), it is also necessary to specialize
the proto::is_callable<> trait. >>*/
: proto::transform<binary_arity>
{
template<typename Expr, typename State, typename Data>
/*<< Transforms have a nested `impl<>` that is
a valid TR1 function object. >>*/
struct impl
: proto::transform_impl<Expr, State, Data>
{
/*<< Get the left and right children. >>*/
typedef typename proto::result_of::left<Expr>::type left_expr;
typedef typename proto::result_of::right<Expr>::type right_expr;
/*<< Apply `CalculatorArity` to find the arity of the left and right children. >>*/
typedef typename boost::result_of<CalculatorArity(left_expr, State, Data)>::type left_arity;
typedef typename boost::result_of<CalculatorArity(right_expr, State, Data)>::type right_arity;
/*<< The return type is the maximum of the children's arities. >>*/
typedef typename mpl::max<left_arity, right_arity>::type result_type;
/*<< The `unary_arity` transform doesn't have an interesting
runtime counterpart, so just return a default-constructed object
of the correct type. >>*/
result_type operator ()(proto::ignore, proto::ignore, proto::ignore) const
{
return result_type();
}
};
};
//]
proto::terminal< placeholder<0> >::type const _1 = {{}};
proto::terminal< placeholder<1> >::type const _2 = {{}};
//[ CalculatorArityGrammar
struct CalculatorArity
: proto::or_<
proto::when< proto::terminal< placeholder<0> >, mpl::int_<1>() >
, proto::when< proto::terminal< placeholder<1> >, mpl::int_<2>() >
, proto::when< proto::terminal<_>, mpl::int_<0>() >
, proto::when< proto::unary_expr<_, _>, unary_arity >
, proto::when< proto::binary_expr<_, _, _>, binary_arity >
>
{};
//]
//[ CalcArity
struct CalcArity
: proto::or_<
proto::when< proto::terminal< placeholder<0> >,
mpl::int_<1>()
>
, proto::when< proto::terminal< placeholder<1> >,
mpl::int_<2>()
>
, proto::when< proto::terminal<_>,
mpl::int_<0>()
>
, proto::when< proto::unary_expr<_, CalcArity>,
CalcArity(proto::_child)
>
, proto::when< proto::binary_expr<_, CalcArity, CalcArity>,
mpl::max<CalcArity(proto::_left),
CalcArity(proto::_right)>()
>
>
{};
//]
// BUGBUG find workaround for this
#if BOOST_WORKAROUND(BOOST_MSVC, == 1310)
#define _pop_front(x) call<proto::_pop_front(x)>
#define _value(x) call<proto::_value(x)>
#endif
//[ AsArgList
// This transform matches function invocations such as foo(1,'a',"b")
// and transforms them into Fusion cons lists of their arguments. In this
// case, the result would be cons(1, cons('a', cons("b", nil()))).
struct ArgsAsList
: proto::when<
proto::function<proto::terminal<_>, proto::vararg<proto::terminal<_> > >
/*<< Use a `reverse_fold<>` transform to iterate over the children
of this node in reverse order, building a fusion list from back to
front. >>*/
, proto::reverse_fold<
/*<< The first child expression of a `function<>` node is the
function being invoked. We don't want that in our list, so use
`pop_front()` to remove it. >>*/
proto::_pop_front(_)
/*<< `nil` is the initial state used by the `reverse_fold<>`
transform. >>*/
, fusion::nil()
/*<< Put the rest of the function arguments in a fusion cons
list. >>*/
, fusion::cons<proto::_value, proto::_state>(proto::_value, proto::_state)
>
>
{};
//]
//[ FoldTreeToList
// This transform matches expressions of the form (_1=1,'a',"b")
// (note the use of the comma operator) and transforms it into a
// Fusion cons list of their arguments. In this case, the result
// would be cons(1, cons('a', cons("b", nil()))).
struct FoldTreeToList
: proto::or_<
// This grammar describes what counts as the terminals in expressions
// of the form (_1=1,'a',"b"), which will be flattened using
// reverse_fold_tree<> below.
proto::when< proto::assign<_, proto::terminal<_> >
, proto::_value(proto::_right)
>
, proto::when< proto::terminal<_>
, proto::_value
>
, proto::when<
proto::comma<FoldTreeToList, FoldTreeToList>
/*<< Fold all terminals that are separated by commas into a Fusion cons list. >>*/
, proto::reverse_fold_tree<
_
, fusion::nil()
, fusion::cons<FoldTreeToList, proto::_state>(FoldTreeToList, proto::_state)
>
>
>
{};
//]
//[ Promote
// This transform finds all float terminals in an expression and promotes
// them to doubles.
struct Promote
: proto::or_<
/*<< Match a `terminal<float>`, then construct a
`terminal<double>::type` with the `float`. >>*/
proto::when<proto::terminal<float>, proto::terminal<double>::type(proto::_value) >
, proto::when<proto::terminal<_> >
/*<< `nary_expr<>` has a pass-through transform which
will transform each child sub-expression using the
`Promote` transform. >>*/
, proto::when<proto::nary_expr<_, proto::vararg<Promote> > >
>
{};
//]
//[ LazyMakePair
struct make_pair_tag {};
proto::terminal<make_pair_tag>::type const make_pair_ = {{}};
// This transform matches lazy function invocations like
// `make_pair_(1, 3.14)` and actually builds a `std::pair<>`
// from the arguments.
struct MakePair
: proto::when<
/*<< Match expressions like `make_pair_(1, 3.14)` >>*/
proto::function<
proto::terminal<make_pair_tag>
, proto::terminal<_>
, proto::terminal<_>
>
/*<< Return `std::pair<F,S>(f,s)` where `f` and `s` are the
first and second arguments to the lazy `make_pair_()` function.
(This uses `proto::make<>` under the covers to evaluate the
transform.)>>*/
, std::pair<
proto::_value(proto::_child1)
, proto::_value(proto::_child2)
>(
proto::_value(proto::_child1)
, proto::_value(proto::_child2)
)
>
{};
//]
namespace lazy_make_pair2
{
//[ LazyMakePair2
struct make_pair_tag {};
proto::terminal<make_pair_tag>::type const make_pair_ = {{}};
// Like std::make_pair(), only as a function object.
/*<<Inheriting from `proto::callable` lets Proto know
that this is a callable transform, so we can use it
without having to wrap it in `proto::call<>`.>>*/
struct make_pair : proto::callable
{
template<typename Sig> struct result;
template<typename This, typename First, typename Second>
struct result<This(First, Second)>
{
typedef
std::pair<
BOOST_PROTO_UNCVREF(First)
, BOOST_PROTO_UNCVREF(Second)
>
type;
};
template<typename First, typename Second>
std::pair<First, Second>
operator()(First const &first, Second const &second) const
{
return std::make_pair(first, second);
}
};
// This transform matches lazy function invocations like
// `make_pair_(1, 3.14)` and actually builds a `std::pair<>`
// from the arguments.
struct MakePair
: proto::when<
/*<< Match expressions like `make_pair_(1, 3.14)` >>*/
proto::function<
proto::terminal<make_pair_tag>
, proto::terminal<_>
, proto::terminal<_>
>
/*<< Return `make_pair()(f,s)` where `f` and `s` are the
first and second arguments to the lazy `make_pair_()` function.
(This uses `proto::call<>` under the covers to evaluate the
transform.)>>*/
, make_pair(
proto::_value(proto::_child1)
, proto::_value(proto::_child2)
)
>
{};
//]
}
//[ NegateInt
struct NegateInt
: proto::when<proto::terminal<int>, proto::negate<_>(_)>
{};
//]
#ifndef BOOST_MSVC
//[ SquareAndPromoteInt
struct SquareAndPromoteInt
: proto::when<
proto::terminal<int>
, proto::_make_multiplies(
proto::terminal<long>::type(proto::_value)
, proto::terminal<long>::type(proto::_value)
)
>
{};
//]
#endif
namespace lambda_transform
{
//[LambdaTransform
template<typename N>
struct placeholder
{
typedef typename N::type type;
static typename N::value_type const value = N::value;
};
// A function object that calls fusion::at()
struct at : proto::callable
{
template<typename Sig>
struct result;
template<typename This, typename Cont, typename Index>
struct result<This(Cont, Index)>
: fusion::result_of::at<
typename boost::remove_reference<Cont>::type
, typename boost::remove_reference<Index>::type
>
{};
template<typename Cont, typename Index>
typename fusion::result_of::at<Cont, Index>::type
operator ()(Cont &cont, Index const &) const
{
return fusion::at<Index>(cont);
}
};
// A transform that evaluates a lambda expression.
struct LambdaEval
: proto::or_<
/*<<When you match a placeholder ...>>*/
proto::when<
proto::terminal<placeholder<_> >
/*<<... call at() with the data parameter, which
is a tuple, and the placeholder, which is an MPL
Integral Constant.>>*/
, at(proto::_data, proto::_value)
>
/*<<Otherwise, use the _default<> transform, which
gives the operators their usual C++ meanings.>>*/
, proto::otherwise< proto::_default<LambdaEval> >
>
{};
// Define the lambda placeholders
proto::terminal<placeholder<mpl::int_<0> > >::type const _1 = {{}};
proto::terminal<placeholder<mpl::int_<1> > >::type const _2 = {{}};
void test_lambda()
{
// a tuple that contains the values
// of _1 and _2
fusion::tuple<int, int> tup(2,3);
// Use LambdaEval to evaluate a lambda expression
int j = LambdaEval()( _2 - _1, 0, tup );
BOOST_CHECK_EQUAL(j, 1);
// You can mutate leaves in an expression tree
proto::literal<int> k(42);
int &l = LambdaEval()( k += 4, 0, tup );
BOOST_CHECK_EQUAL(k.get(), 46);
BOOST_CHECK_EQUAL(&l, &k.get());
// You can mutate the values in the tuple, too.
LambdaEval()( _1 += 4, 0, tup );
BOOST_CHECK_EQUAL(6, fusion::at_c<0>(tup));
}
//]
}
void test_examples()
{
//[ CalculatorArityTest
int i = 0; // not used, dummy state and data parameter
std::cout << CalculatorArity()( proto::lit(100) * 200, i, i) << '\n';
std::cout << CalculatorArity()( (_1 - _1) / _1 * 100, i, i) << '\n';
std::cout << CalculatorArity()( (_2 - _1) / _2 * 100, i, i) << '\n';
//]
BOOST_CHECK_EQUAL(0, CalculatorArity()( proto::lit(100) * 200, i, i));
BOOST_CHECK_EQUAL(1, CalculatorArity()( (_1 - _1) / _1 * 100, i, i));
BOOST_CHECK_EQUAL(2, CalculatorArity()( (_2 - _1) / _2 * 100, i, i));
BOOST_CHECK_EQUAL(0, CalcArity()( proto::lit(100) * 200, i, i));
BOOST_CHECK_EQUAL(1, CalcArity()( (_1 - _1) / _1 * 100, i, i));
BOOST_CHECK_EQUAL(2, CalcArity()( (_2 - _1) / _2 * 100, i, i));
using boost::fusion::cons;
using boost::fusion::nil;
cons<int, cons<char, cons<std::string> > > args(ArgsAsList()( _1(1, 'a', std::string("b")), i, i ));
BOOST_CHECK_EQUAL(args.car, 1);
BOOST_CHECK_EQUAL(args.cdr.car, 'a');
BOOST_CHECK_EQUAL(args.cdr.cdr.car, std::string("b"));
cons<int, cons<char, cons<std::string> > > lst(FoldTreeToList()( (_1 = 1, 'a', std::string("b")), i, i ));
BOOST_CHECK_EQUAL(lst.car, 1);
BOOST_CHECK_EQUAL(lst.cdr.car, 'a');
BOOST_CHECK_EQUAL(lst.cdr.cdr.car, std::string("b"));
proto::plus<
proto::terminal<double>::type
, proto::terminal<double>::type
>::type p = Promote()( proto::lit(1.f) + 2.f, i, i );
//[ LazyMakePairTest
int j = 0; // not used, dummy state and data parameter
std::pair<int, double> p2 = MakePair()( make_pair_(1, 3.14), j, j );
std::cout << p2.first << std::endl;
std::cout << p2.second << std::endl;
//]
BOOST_CHECK_EQUAL(p2.first, 1);
BOOST_CHECK_EQUAL(p2.second, 3.14);
std::pair<int, double> p3 = lazy_make_pair2::MakePair()( lazy_make_pair2::make_pair_(1, 3.14), j, j );
std::cout << p3.first << std::endl;
std::cout << p3.second << std::endl;
BOOST_CHECK_EQUAL(p3.first, 1);
BOOST_CHECK_EQUAL(p3.second, 3.14);
NegateInt()(proto::lit(1), i, i);
#ifndef BOOST_MSVC
SquareAndPromoteInt()(proto::lit(1), i, i);
#endif
lambda_transform::test_lambda();
}
using namespace boost::unit_test;
///////////////////////////////////////////////////////////////////////////////
// init_unit_test_suite
//
test_suite* init_unit_test_suite( int argc, char* argv[] )
{
test_suite *test = BOOST_TEST_SUITE("test examples from the documentation");
test->add(BOOST_TEST_CASE(&test_examples));
return test;
}
