C ++ ptr_fun没有找到void参数化函数

Question

I tried using the std::ptr_fun to wrap my function, but when I try to wrap a function with void parameter and bool return type I end up with an error:

code:

std::function<bool()> cr = std::not1(std::ptr_fun(&funct1));

function:

bool funct1()      
{                  
    return false;     
}

the error:

error: no matching function for call to 'ptr_fun(bool (*)())'

but whenever I change the parameter to int, the problem seems to go away.

how do I wrap a function with a void parameter?

Answer 1

std::ptr_fun only works on unary functions: functions with exactly one parameter.

bool funct1(); is not a unary function, it is a nullary function. There is no such thing as a void parameter. The syntax bool funct1(void); inherited from C is just a strange way of saying there are no parameters at all.