定义的模板C++

这是一个noob问题抱歉:( 我不知道为什么这给了我一个error..could有人请解释例如我想做的事：定义的模板C++

vector<double> a; 
string s("0.11 11.0002"); 
copys(s, a); 


template <typename T, typename S> 
void copys(T& c, S& d) 
{ 
    istringstream iss(c); 
    copy(istream_iterator<S>(iss), istream_iterator<S>(), 
     back_inserter(d)); 
    return; 
}

错误从编译器：

/usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stream_iterator.h: In member function `void std::istream_iterator<_Tp, _CharT, _Trai 
    ts, _Dist>::_M_read() [with _Tp = std::vector<double, std::allocator<double> >, _CharT = char, _Traits = std::char_traits<char>, _Dist 
    = int]': 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stream_iterator.h:68: instantiated from `std::istream_iterator<_Tp, _CharT, _Trait 
    s, _Dist>::istream_iterator(std::basic_istream<_CharT, _Traits>&) [with _Tp = std::vector<double, std::allocator<double> >, _CharT = ch 
    ar, _Traits = std::char_traits<char>, _Dist = int]' 
    ProfitCalculator.cpp:20: instantiated from `void copys(T&, S&) [with T = std::basic_string<char, std::char_traits<char>, std::allocat 
    or<char> >, S = std::vector<double, std::allocator<double> >]' 
    ProfitCalculator.cpp:41: instantiated from here 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stream_iterator.h:119: error: no match for `operator>>' in `*((std::istream_iterator 
    <std::vector<double, std::allocator<double> >, char, std::char_traits<char>, int>*)this)->std::istream_iterator<std::vector<double, std 
    ::allocator<double> >, char, std::char_traits<char>, int>::_M_stream >> ((std::istream_iterator<std::vector<double, std::allocator<doub 
    le> >, char, std::char_traits<char>, int>*)this)->std::istream_iterator<std::vector<double, std::allocator<double> >, char, std::char_t 
    raits<char>, int>::_M_value' 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:123: note: candidates are: std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>& (*)(std::basic_istream<_CharT, _Traits>&)) [with _CharT = char, _Tr 
    aits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:127: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(std::basic_ios<_CharT, _Traits>& (*)(std::basic_ios<_CharT, _Traits>&)) [with _CharT = char, _Traits = s 
    td::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:134: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:170: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(bool&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:174: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(short int&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:177: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:181: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(int&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:184: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:188: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(long int&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:192: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:197: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:201: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:206: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(float&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:210: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(double&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:214: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(long double&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:218: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(void*&) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/istream:242: note:     std::basic_istream<_CharT, _Traits>& std::basic_istrea 
    m<_CharT, _Traits>::operator>>(std::basic_streambuf<_CharT, _Traits>*) [with _CharT = char, _Traits = std::char_traits<char>] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_algobase.h: In static member function `static _OI std::__copy_move<<anonymous>, 
    <anonymous>, <template-parameter-1-3> >::__copy_m(_II, _II, _OI) [with _II = std::istream_iterator<std::vector<double, std::allocator<d 
    ouble> >, char, std::char_traits<char>, int>, _OI = std::back_insert_iterator<std::vector<double, std::allocator<double> > >, bool <ano 
    nymous> = false, bool <anonymous> = false, <template-parameter-1-3> = std::input_iterator_tag]': 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_algobase.h:396: instantiated from `_OI std::__copy_move_a(_II, _II, _OI) [with 
    bool _IsMove = false, _II = std::istream_iterator<std::vector<double, std::allocator<double> >, char, std::char_traits<char>, int>, _O 
    I = std::back_insert_iterator<std::vector<double, std::allocator<double> > >]' 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_algobase.h:435: instantiated from `_OI std::__copy_move_a2(_II, _II, _OI) [wit 
    h bool _IsMove = false, _II = std::istream_iterator<std::vector<double, std::allocator<double> >, char, std::char_traits<char>, int>, _ 
    OI = std::back_insert_iterator<std::vector<double, std::allocator<double> > >]' 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_algobase.h:466: instantiated from `_OI std::copy(_II, _II, _OI) [with _II = st 
    d::istream_iterator<std::vector<double, std::allocator<double> >, char, std::char_traits<char>, int>, _OI = std::back_insert_iterator<s 
    td::vector<double, std::allocator<double> > >]' 
    ProfitCalculator.cpp:20: instantiated from `void copys(T&, S&) [with T = std::basic_string<char, std::char_traits<char>, std::allocat 
    or<char> >, S = std::vector<double, std::allocator<double> >]' 
    ProfitCalculator.cpp:41: instantiated from here 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_algobase.h:312: error: no match for `operator=' in `__result.std::back_insert_it 
    erator<_Container>::operator* [with _Container = std::vector<double, std::allocator<double> >]() = __first.std::istream_iterator<_Tp, _ 
    CharT, _Traits, _Dist>::operator* [with _Tp = std::vector<double, std::allocator<double> >, _CharT = char, _Traits = std::char_traits<c 
    har>, _Dist = int]()' 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_iterator.h:412: note: candidates are: std::back_insert_iterator<_Container>& std 
    ::back_insert_iterator<_Container>::operator=(typename _Container::const_reference) [with _Container = std::vector<double, std::allocat 
    or<double> >] 
    /usr/lib/gcc/i686-pc-cygwin/4.3.4/include/c++/bits/stl_iterator.h:388: note:     std::back_insert_iterator<std::vector<doub 
    le, std::allocator<double> > >& std::back_insert_iterator<std::vector<double, std::allocator<double> > >::operator=(const std::back_ins 
    ert_iterator<std::vector<double, std::allocator<double> > >&) 
    make: *** [ProfitCalculator] Error 1

来源

2011-02-11 ardiyu07

你得到什么错误？ – 2011-02-11 16:08:41

正如弗雷德所问，你有什么错误？另外，将模板定义移到顶部（在使用之前）。 – Steve 2011-02-11 16:13:17

的问题是，模板替换后，该

copy(istream_iterator<S>(iss), istream_iterator<S>(), 
     back_inserter(d));

成为

copy(istream_iterator<vector<double> >(iss), istream_iterator<vector<double> >(), 
         ^^^^^^^^^^^^^^^       ^^^^^^^^^^^^^^^ 
     back_inserter(d));

你不希望从字符串中提取vector<double> -S（和stringstreams不能这样做呢）。相反，您希望从字符串中提取double -s，因此您需要矢量的value_type（在这种情况下为double）。

typedef typename S::value_type value_type; 
copy(istream_iterator<value_type>(iss), istream_iterator<value_type>(), 
     back_inserter(d));

来源

2011-02-11 16:32:46 UncleBens

很难肯定地说没有错误，但我看到两个潜在的问题：

您的模板定义在使用后出现，因此编译器不知道copys(...)应该是什么。
a vector<double>不能.push_back(std::string)，并且copys什么也没有，我可以看到什么将从字符串表示转换为双。

更新：好吧，给你的问题的错误，我想说的答案是＃2。

来源

2011-02-11 16:20:53

定义的模板C++

回答

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