boost::proto::fold_tree< Sequence, State0, Fun > Struct Template Reference

A PrimitiveTransform that recursively applies the fold<> transform to sub-trees that all share a common tag type. More...

#include <fold_tree.hpp>

Inheritance diagram for boost::proto::fold_tree< Sequence, State0, Fun >:

Collaboration diagram for boost::proto::fold_tree< Sequence, State0, Fun >:

Classes
struct	impl
struct	impl< Expr &, State, Data >

Public Types
typedef fold_tree< Sequence, State0, Fun >	transform_type

Public Member Functions
	BOOST_PROTO_CALLABLE () typedef X proto_is_transform_
BOOST_FORCEINLINE boost::proto::detail::apply_transform < transform_type(Expr const &)> ::result_type	operator() (Expr &&e) const
BOOST_FORCEINLINE boost::proto::detail::apply_transform < transform_type(Expr const &, State const &)> ::result_type	operator() (Expr &&e, State &&s) const
BOOST_FORCEINLINE boost::proto::detail::apply_transform < transform_type(Expr const &, State const &, Data const &)> ::result_type	operator() (Expr &&e, State &&s, Data &&d) const

Detailed Description

template<typename Sequence, typename State0, typename Fun>
struct boost::proto::fold_tree< Sequence, State0, Fun >

A PrimitiveTransform that recursively applies the fold<> transform to sub-trees that all share a common tag type.

fold_tree<> is useful for flattening trees into lists; for example, you might use fold_tree<> to flatten an expression tree like a | b | c into a Fusion list like cons(c, cons(b, cons(a))).

fold_tree<> is easily understood in terms of a recurse_if_<> helper, defined as follows:

template<typename Tag, typename Fun>
struct recurse_if_
  : if_<
        // If the current node has type "Tag" ...
        is_same<tag_of<_>, Tag>()
        // ... recurse, otherwise ...
      , fold<_, _state, recurse_if_<Tag, Fun> >
        // ... apply the Fun transform.
      , Fun
    >
{};

With recurse_if_<> as defined above, fold_tree<Sequence, State0, Fun>()(e, s, d) is equivalent to fold<Sequence, State0, recurse_if_<Expr::proto_tag, Fun> >()(e, s, d). It has the effect of folding a tree front-to-back, recursing into child nodes that share a tag type with the parent node.

Member Typedef Documentation

typedef fold_tree< Sequence, State0, Fun > boost::proto::transform< fold_tree< Sequence, State0, Fun > , X >::transform_type

inherited

Member Function Documentation

boost::proto::transform< fold_tree< Sequence, State0, Fun > , X >::BOOST_PROTO_CALLABLE ( )

inherited

BOOST_FORCEINLINE boost::proto::detail::apply_transform<transform_type(Expr const &, State const &, Data const &)>::result_type boost::proto::transform< fold_tree< Sequence, State0, Fun > , X >::operator() ( Expr &&  e, State &&  s, Data &&  d  ) const

inlineinherited

BOOST_FORCEINLINE boost::proto::detail::apply_transform<transform_type(Expr const &, State const &)>::result_type boost::proto::transform< fold_tree< Sequence, State0, Fun > , X >::operator() ( Expr &&  e, State &&  s  ) const

inlineinherited

BOOST_FORCEINLINE boost::proto::detail::apply_transform<transform_type(Expr const &)>::result_type boost::proto::transform< fold_tree< Sequence, State0, Fun > , X >::operator() ( Expr &&  e ) const

inlineinherited

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The documentation for this struct was generated from the following file:

• boost_1_57_0/boost/proto/proto_fwd.hpp