Update of /cvsroot/boost/boost/libs/xpressive/proto/example
In directory sc8-pr-cvs3.sourceforge.net:/tmp/cvs-serv12318
Modified Files:
Jamfile.v2
Added Files:
vec3.cpp
Log Message:
port Vec3 example from PETE
--- NEW FILE: vec3.cpp ---
///////////////////////////////////////////////////////////////////////////////
// Copyright 2007 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)
//
// This is a simple example using proto::extends to extend a terminal type with
// additional behaviors, and using custom contexts and proto::eval for
// evaluating expressions. It is a port of the Vec3 example
// from PETE (http://www.codesourcery.com/pooma/download.html).
#include <iostream>
#include <boost/xpressive/proto/proto.hpp>
#include <boost/xpressive/proto/context.hpp>
#include <boost/xpressive/proto/proto_typeof.hpp>
using namespace boost::proto;
// Here is an evaluation context that indexes into a Vec3
// expression, and combines the result.
struct Vec3SubscriptCtx
: callable_context< Vec3SubscriptCtx const >
{
typedef int result_type;
Vec3SubscriptCtx(int i)
: i_(i)
{}
// Index array terminals with our subscript. Everything
// else will be handled by the default evaluation context.
int operator()(tag::terminal, int const (&arr)[3]) const
{
return arr[this->i_];
}
int i_;
};
// Here is an evaluation context that counts the number of
// Vec3 terminals in an expression.
struct CountLeavesCtx
: callable_context< CountLeavesCtx >
{
typedef int result_type;
CountLeavesCtx()
: count(0)
{}
int operator()(tag::terminal, int const (&)[3])
{
++this->count;
return 0; // not used
}
int count;
};
// Here is the Vec3 struct, which is a vector of 3 integers.
struct Vec3
: extends<terminal<int[3]>::type, Vec3>
{
explicit Vec3(int i=0, int j=0, int k=0)
{
(*this)[0] = i;
(*this)[1] = j;
(*this)[2] = k;
}
int &operator[](int i)
{
return arg(*this)[i];
}
int const &operator[](int i) const
{
return arg(*this)[i];
}
// Here we define a operator= for Vec3 terminals that
// takes a Vec3 expression.
template< typename Expr >
Vec3 &operator =(Expr const & expr)
{
typedef Vec3SubscriptCtx const CVec3SubscriptCtx;
(*this)[0] = eval(as_expr(expr), CVec3SubscriptCtx(0));
(*this)[1] = eval(as_expr(expr), CVec3SubscriptCtx(1));
(*this)[2] = eval(as_expr(expr), CVec3SubscriptCtx(2));
return *this;
}
void print() const
{
std::cout << '{' << (*this)[0]
<< ", " << (*this)[1]
<< ", " << (*this)[2]
<< '}' << std::endl;
}
};
// The count_leaves() function uses the CountLeavesCtx and
// proto::eval() to count the number of leaves in an expression.
template<typename Expr>
int count_leaves(Expr const &expr)
{
CountLeavesCtx ctx;
eval(expr, ctx);
return ctx.count;
}
int main()
{
Vec3 a, b, c;
c = 4;
b[0] = -1;
b[1] = -2;
b[2] = -3;
a = b + c;
a.print();
Vec3 d;
BOOST_PROTO_AUTO(expr1, b + c);
d = expr1;
d.print();
int num = count_leaves(expr1);
std::cout << num << std::endl;
BOOST_PROTO_AUTO(expr2, b + 3 * c);
num = count_leaves(expr2);
std::cout << num << std::endl;
BOOST_PROTO_AUTO(expr3, b + c * d);
num = count_leaves(expr3);
std::cout << num << std::endl;
return 0;
}
Index: Jamfile.v2
===================================================================
RCS file: /cvsroot/boost/boost/libs/xpressive/proto/example/Jamfile.v2,v
retrieving revision 1.4
retrieving revision 1.5
diff -u -d -r1.4 -r1.5
--- Jamfile.v2 23 Jun 2007 01:38:40 -0000 1.4
+++ Jamfile.v2 23 Jun 2007 06:32:01 -0000 1.5
@@ -37,3 +37,8 @@
:
rgb.cpp
;
+
+exe vec3
+ :
+ vec3.cpp
+ ;
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