Home » U++ Library support » U++ Core » _pick understanding
| _pick understanding [message #26369] |
Tue, 27 April 2010 21:08  |
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kohait00
Messages: 939
Registered: July 2009
Location: Germany
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Experienced Contributor |
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hi there,
in
http://www.ultimatepp.org/srcdoc$Core$pick_$en-us.html
there is _pick explained as
but when i look in code the _pick definition in MSC environment is empty.. why? setting it to const there as well compiles well..
is there any thing special to MSC to consider? just out of curiosity..
Defs.h:277
#ifdef COMPILER_MSC
#define pick_
#else
#define pick_ const
#endif
another question:
Topt.h:252
template <class T, class B = EmptyClass>
class DeepCopyOption : public B {
public:
friend T& operator<<=(T& dest, const T& src)
{ if(&dest != &src) { (&dest)->T::~T(); ::new(&dest) T(src, 1); } return dest; }
friend void DeepCopyConstruct(void *dest, const T& src)
{ ::new (dest) T(src, 0); }
friend T *DeepCopyNew(const T& src)
{ return ::new T(src, 0); }
};
uses 1 for param in <<= operator while link above also states that the second int parameter is just for distinciton and ignored. is it evaluated anywhere? maybe to indicate a reuse??
IMHO _pick should be explained a bit better, i understand the problem leading to _pick solution, but especially the explanation
| Quote: |
C++ disallows binding temporaries to non-const references - and that is unfortunately just the thing we need to do here, as we need to change the source temporary returned from a function.
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should be visualised by a (not permitted) code snippet as well.
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