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Yess we can! Invented a statical duck-detector!

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This commit is contained in:
Fischlurch 2010-01-02 06:26:56 +01:00
parent e94927d5a3
commit f517cfb19a
1 changed files with 49 additions and 40 deletions
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89
src/tool/try.cpp
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@ -14,6 +14,7 @@
// 10/8 - abusing the STL containers to hold noncopyable values
// 6/09 - investigating how to build a mixin template providing an operator bool()
// 12/9 - tracking down a strange "warning: type qualifiers ignored on function return type"
// 1/10 - can we determine at compile time the presence of a certain function (for duck-typing)?
//#include <nobug.h>
@ -21,7 +22,6 @@
//#include "include/logging.h"
//#include "include/nobugcfg.h"
#include <tr1/functional>
#include <iostream>
//#include <typeinfo>
@ -30,47 +30,59 @@
#include <cstdio>
//using std::tr1::bind;
using std::tr1::placeholders::_1;
//using std::rand;
using std::string;
using std::cout;
using std::endl;
template <typename SEQ, typename Oper>
inline bool
eat_all (SEQ& coll, Oper predicate)
struct A
{
typename SEQ::const_iterator e = coll.end();
typename SEQ::const_iterator i = coll.begin();
for ( ; i!=e; ++i )
if (!predicate(*i))
return false;
return true;
}
template < typename CON, typename FUN
, typename P1
, typename P2
>
inline bool
eat_all (CON& elements, FUN function, P1 bind1, P2 bind2)
int& funA ();
};
struct B
{
return eat_all (elements, std::tr1::bind<bool> (function, bind1, bind2));
}
void funA();
};
typedef char Yes_t;
struct No_t { char padding[8]; };
template<typename TY>
class Detector1
{
template<typename X, int i = sizeof(&X::funA)>
struct Probe
{ };
template<class X>
static Yes_t check(Probe<X>*);
template<class>
static No_t check(...);
public:
static const bool value = (sizeof(Yes_t)==sizeof(check<TY>(0)));
};
bool
plainFunc (int i, int j)
{
cout <<':'<< i+j;
return i+j;
}
template<typename TY>
class Detector2
{
template<typename X, int& (X::*)(void)>
struct Probe
{ };
template<class X>
static Yes_t check(Probe<X,&X::funA>*);
template<class>
static No_t check(...);
public:
static const bool value = (sizeof(Yes_t)==sizeof(check<TY>(0)));
};
int
@ -79,14 +91,11 @@ main (int, char**)
// NOBUG_INIT;
typedef std::vector<int> VecI;
cout << "Detector1<A> = " << Detector1<A>::value << endl;
cout << "Detector1<B> = " << Detector1<B>::value << endl;
uint count = 4;
VecI numberz;
while (count)
numberz.push_back(count--);
eat_all (numberz, plainFunc, 10, _1 );
cout << "Detector2<A> = " << Detector2<A>::value << endl;
cout << "Detector2<B> = " << Detector2<B>::value << endl;
cout << "\n.gulp.\n";