Function left

boost::proto::left — Return the left child of the specified binary Proto expression.

Synopsis

// In header: <boost/proto/traits.hpp>


template<typename Expr> 
  typename proto::result_of::left< Expr & >::type left(Expr & expr);
template<typename Expr> 
  typename proto::result_of::left< Expr const & >::type 
  left(Expr const & expr);

Description

Return the left child of the specified binary Proto expression. The child is returned by reference.

Requires:

proto::is_expr<Expr>::value is true.

2 == Expr::proto_arity::value

Returns:

A reference to the left child of expr.

Throws:

Will not throw.