Re: [Boost-users] calc2_ast.cpp

Subject: Re: [Boost-users] calc2_ast.cpp
From: Larry Evans (cppljevans_at_[hidden])
Date: 2013-10-02 13:24:24

On 10/02/13 12:13, Olivier Austina wrote:
> Hi,
> this is a basic question (I am sorry).
> I am try to undestand the  calc2_ast.cpp example at
> http://www.boost.org/doc/libs/1_41_0/libs/spirit/example/qi/calc2_ast.cpp
> I think the instruction expression_ast() : expr(nil()){} is an
> inheritance.
expr is a member variable of expression_ast.
> Where can I find the definition of expr()?
See below.
> This is the code
> struct expression_ast
>      {
>          typedef
>              boost::variant<
>                  nil // can't happen!
>                , unsigned int
>                , boost::recursive_wrapper<expression_ast>
>                , boost::recursive_wrapper<binary_op>
>                , boost::recursive_wrapper<unary_op>
>              >
>          type;
>
> *expression_ast() : expr(nil()){};*
>
>          template <typename Expr>
>          expression_ast(Expr const& expr)
>            : expr(expr) {}
>
>          expression_ast& operator+=(expression_ast const& rhs);
>          expression_ast& operator-=(expression_ast const& rhs);
>          expression_ast& operator*=(expression_ast const& rhs);
>          expression_ast& operator/=(expression_ast const& rhs);
>
>          type expr;
Here's the definition of expr.
>      };
>
>      //expression_ast bbb;
>      struct binary_op
>      {
>          binary_op(
>              char op
>            , expression_ast const& left
>            , expression_ast const& right)
>          : op(op), left(left), right(right) {}
>
>          char op;
>          expression_ast left;
>          expression_ast right;
>      };
>
>
> Thank you.
>
>
>
> Regards
> Olivier
>
>
>
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