提升绑定功能参考

Question

我在编译以下代码段时遇到问题

int temp; 
vector<int> origins;

vector<string> originTokens = OTUtils::tokenize(buffer, ","); // buffer is a char[] array

// original loop 
BOOST_FOREACH(string s, originTokens)
{
    from_string(temp, s);
    origins.push_back(temp);
}    

// I'd like to use this to replace the above loop
std::transform(originTokens.begin(), originTokens.end(), origins.begin(), boost::bind<int>(&FromString<int>, boost::ref(temp), _1));

所涉及的功能在哪里

// the third parameter should be one of std::hex, std::dec or std::oct
template <class T>
bool FromString(T& t, const std::string& s, std::ios_base& (*f)(std::ios_base&) = std::dec)
{
    std::istringstream iss(s);
    return !(iss >> f >> t).fail();
}

我得到的错误是

1>Compiling with Intel(R) C++ 11.0.074 [IA-32]... (Intel C++ Environment)
1>C:\projects\svn\bdk\Source\deps\boost_1_42_0\boost/bind/bind.hpp(303): internal error: assertion failed: copy_default_arg_expr: rout NULL, no error (shared/edgcpfe/il.c, line 13919)
1>
1>          return unwrapper<F>::unwrap(f, 0)(a[base_type::a1_], a[base_type::a2_]);
1>                                                                                ^
1>
1>icl: error #10298: problem during post processing of parallel object compilation

谷歌非常无益,所以我希望这里的一些人可以提供一些见解.

更新:问题由@ gf的解决方案回答,但有趣的是原始函数不太正确,因为它存储了转换操作的结果(失败/未失败)而不是转换后的值本身.我更改了签名直接返回转换后的值,编译器能够正确推断绑定的类型.

// new signature
T FromString(const std::string& s, std::ios_base& (*f)(std::ios_base&) = std::dec);

// revised calling syntax - note that bind<int> is not required. 
transform(originTokens.begin(), originTokens.end(), origins.begin(),  bind(&FromString<int>, _1, std::dec));

Answer 1

FromString()需要3个参数,默认参数不是函数类型的一部分.所以绑定表达式可能应该是这样的:

boost::bind<int>(&FromString<int>, boost::ref(temp), _1, std::dec);