| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"" |
| Date: |
07 Mar 2005 01:09:16 PM |
| Object: |
query on std::make_pair() |
Hi there, the C++ standard (section 20.2) defines std::make_pair() as:
template <class T1, class T2>
pair<T1, T2> make_pair(const T1& x, const T2& y);
On my system (.NET 2003) it is defined as:
template<class _Ty1, class _Ty2> inline
pair<_Ty1, _Ty2> __cdecl make_pair(_Ty1 _Val1, _Ty2 _Val2)
{
// return pair composed from arguments
return (pair<_Ty1, _Ty2>(_Val1, _Val2));
}
In particular, not that the arguments _Val1 and _Val2 are passed in by
value, and not by reference.
Is this a bug in the .NET library? or is this actually allowed by the
spec?
.
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| User: "Pete Becker" |
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| Title: Re: query on std::make_pair() |
07 Mar 2005 01:21:26 PM |
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wrote:
Hi there, the C++ standard (section 20.2) defines std::make_pair() as:
template <class T1, class T2>
pair<T1, T2> make_pair(const T1& x, const T2& y);
On my system (.NET 2003) it is defined as:
template<class _Ty1, class _Ty2> inline
pair<_Ty1, _Ty2> __cdecl make_pair(_Ty1 _Val1, _Ty2 _Val2)
{
// return pair composed from arguments
return (pair<_Ty1, _Ty2>(_Val1, _Val2));
}
In particular, not that the arguments _Val1 and _Val2 are passed in by
value, and not by reference.
Is this a bug in the .NET library? or is this actually allowed by the
spec?
That was changed in the 2003 revision of the standard. It now says
template < class T1 , class T2 >
pair <T1 , T2 > make_pair (T1 x , T2 y );
7 Returns: pair<T1, T2>(x, y).
--
Pete Becker
Dinkumware, Ltd. (http://www.dinkumware.com)
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| User: "" |
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| Title: Re: query on std::make_pair() |
07 Mar 2005 02:48:03 PM |
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very interesting - what is the reason for this change?
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| User: "Pete Becker" |
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| Title: Re: query on std::make_pair() |
07 Mar 2005 03:01:28 PM |
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wrote:
very interesting - what is the reason for this change?
make_pair("abc", 3);
used to be illegal, because the first argument creates a reference to an
array, which can't be copied. With the new version the type of the first
argument decays to pointer to const char.
--
Pete Becker
Dinkumware, Ltd. (http://www.dinkumware.com)
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