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Design: extend the Variant::Visitor (3)

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specialise to a predicate working on const types.

This is the complete draft we want to integrate into
the existing Visitor code
This commit is contained in:
Fischlurch 2015-08-29 18:10:18 +02:00
parent 92b779c6b8
commit d6e9d5b3a4
1 changed files with 61 additions and 10 deletions
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71
research/try.cpp
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@ -48,12 +48,13 @@ typedef unsigned int uint;
#include "lib/meta/typelist.hpp"
#include "lib/meta/generator.hpp"
#include "lib/format-util.hpp"
#include "lib/util.hpp"
//#include <functional>
#include <iostream>
#include <cstdarg>
#include <string>
using util::unConst;
using std::string;
using std::cout;
using std::endl;
@ -75,6 +76,25 @@ struct VFunc
};
using lib::meta::NullType;
using lib::meta::Node;
template<typename TYPES>
struct ConstAll;
template<>
struct ConstAll<NullType>
{
typedef NullType List;
};
template<typename TY, typename TYPES>
struct ConstAll<Node<TY,TYPES>>
{
typedef Node<const TY, typename ConstAll<TYPES>::List> List;
};
template<class A, class B>
struct Var
@ -85,17 +105,37 @@ struct Var
using TYPES = lib::meta::Types<A,B>;
template<typename RET>
using Visitor = typename VFunc<RET>::template VisitorInterface<TYPES>;
using VisitorFunc = typename VFunc<RET>::template VisitorInterface<TYPES>;
template<typename RET>
using VisitorConstFunc = typename VFunc<RET>::template VisitorInterface<ConstAll<typename TYPES::List>>;
using Visitor = VisitorFunc<void>;
using Predicate = VisitorConstFunc<bool>;
template<typename RET>
RET
accept (Visitor<RET>& visitor)
accept (VisitorFunc<RET>& visitor)
{
typename VFunc<RET>::template ValueAcceptInterface<A>& visA = visitor;
typename VFunc<RET>::template ValueAcceptInterface<B>& visB = visitor;
visA.handle (a);
return visB.handle (b);
}
void
accept (Visitor& visitor)
{
accept<void> (visitor);
}
bool
accept (Predicate& visitor) const
{
typename VFunc<bool>::template ValueAcceptInterface<const A>& visA = visitor;
typename VFunc<bool>::template ValueAcceptInterface<const B>& visB = visitor;
return visA.handle (a)
&& visB.handle (b);
}
operator string() const
@ -109,25 +149,36 @@ struct Var
};
using V = Var<int, string>;
class Visi
: public Var<int,string>::Visitor<void>
: public V::Visitor
{
virtual void handle(int& i) { ++i; }
virtual void handle(string& s) { s += ".."; }
virtual void handle(int& i) { ++i; }
virtual void handle(string& s) { s += "."; }
};
class Predi
: public V::Predicate
{
virtual bool handle(int const& i) { return 0 == i % 2; }
virtual bool handle(string const& s) { return 0 == s.length() % 2; }
};
int
main (int, char**)
{
using V = Var<int, string>;
V var{12, "hui"};
V var{12, "huii"};
cout << string(var)<<endl;
Visi visi;
var.accept<void>(visi);
Predi predi;
cout << var.accept(predi) <<endl;
var.accept(visi);
cout << var.accept(predi) <<endl;
cout << string(var)<<endl;
cout << "\n.gulp.\n";