I'm working through "A Tour of C++" by BS, and am recreating the Vector
class that he uses throughout, at least the first four chapters.
I hit a snag building the second version of the Vector
constructor with a std::initializer_list
. A static_cast<int>
is used to convert the size_type
to an int
so sz
of my Vector
can be initialized.
But, for some reason, when I try to compile it on my personal machine and OnlineGDB, I get an error:
main.cpp: In constructor 'Vector::Vector(std::initializer_list<double>)': main.cpp:24:58: error: invalid conversion from ‘std::initializer_list::size_type {aka long unsigned int}’ to ‘double*’ [-fpermissive] :elem{lst.size()}, sz{static_cast<int>( lst.size() )} ^
Why is it trying to convert the size_type
to a double*
? Should it not simply be converting it to a regular int
?
Please see my attempt at a minimal reproducible example below.
#include <algorithm>
#include <initializer_list>
class Vector{
double* elem;
int sz;
public:
Vector(std::initializer_list<double> lst)
:elem{lst.size()}, sz{static_cast<int>( lst.size() )}
{
std::copy(lst.begin(), lst.end(), elem);
}
};
int main()
{
Vector vec = {1.2, 1.3, 1.4};
return 0;
}
Here
elem{lst.size()}
you are initializing adouble*
using asize_t
.And why do you do
static_cast<int>( lst.size() )
? Your size should be of the same type as the size of the list, which issize_t
, to avoid negative sizes.Here is your code after some editing:
Live