Update of /cvsroot/boost/boost/libs/xpressive/proto/example
In directory
sc8-pr-cvs3.sourceforge.net:/tmp/cvs-serv20242/libs/xpressive/proto/example
Modified Files:
vector.cpp
Log Message:
add null_context, use in vector.cpp example
Index: vector.cpp
===================================================================
RCS file: /cvsroot/boost/boost/libs/xpressive/proto/example/vector.cpp,v
retrieving revision 1.1
retrieving revision 1.2
diff -u -d -r1.1 -r1.2
--- vector.cpp 25 Jun 2007 05:40:42 -0000 1.1
+++ vector.cpp 25 Jun 2007 07:44:54 -0000 1.2
@@ -53,25 +53,33 @@
// Here is an evaluation context that verifies that all the
// vectors in an expression have the same size.
struct VectorSizeCtx
- : proto::callable_context< VectorSizeCtx const >
{
- typedef int result_type;
-
VectorSizeCtx(std::size_t size)
: size_(size)
{}
+ // Unless this is a vector terminal, use the
+ // null evaluation context
+ template<typename Expr, typename Arg = typename
proto::result_of::arg<Expr>::type>
+ struct eval
+ : proto::null_eval<Expr, VectorSizeCtx const>
+ {};
+
// Index array terminals with our subscript. Everything
// else will be handled by the default evaluation context.
- template<typename T, typename A>
- int operator()(proto::tag::terminal, std::vector<T, A> const &arr) const
+ template<typename Expr, typename T, typename A>
+ struct eval<Expr, std::vector<T, A> >
{
- if(this->size_ != arr.size())
+ typedef void result_type;
+
+ result_type operator()(Expr &expr, VectorSizeCtx const &ctx) const
{
- throw std::invalid_argument("LHS and RHS are not compatible");
+ if(ctx.size_ != proto::arg(expr).size())
+ {
+ throw std::invalid_argument("LHS and RHS are not compatible");
+ }
}
- return 0; // not used
- }
+ };
std::size_t size_;
};
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