let contents : Vec<char> = read_file!(file_name).chars().collect();
Why do I have to specify like the Vec<char> type annotation? I have seen this in the following case too:
let args : Vec<String> = std::env::args().collect();
Is this something related to .collect() method ?? I'm really confused here
struct S
{
int a,b,c;
int* ptr;
};
void print_bytes(S* ptr)
{
unsigned char* base = (unsigned char*)ptr;
for(size_t i=0;i<sizeof(S);i++) std::cout << int(base[i]) << ' ';
std::cout << '\n';
}
I was watching a talk on type punning where they used this example and the argument was something like the base pointer isnt guareneteed to be pointing to the first byte of the object and that accessing it like an array of chars is wrong because there was no array of chars there just an object of type S which honestly makes sense and doesn't at the same time. Can anyone explain whats' going on here?
https://www.youtube.com/watch?v=_qzMpk-22cc
45th minute onwards is where this example is talked about
#include<iostream>
#include<print>
#include<vector>
struct S
{
constexpr S(int n) : vec(n,0) {}
constexpr auto get_vec() const {return vec;}
std::vector<int> vec;
};
constexpr auto foo()
{
constexpr S s(2);
// here is where the error comes which I don't understand
//‘S(2)’ is not a constant expression because it refers to a //result of ‘operator new’
// 193 | return static_cast<_Tp*>(::operator // new(__n));
//
constexpr auto my_vec = s.get_vec();
for(const auto& el: my_vec)
{
std::cout << el << ' ';
}
std::cout << '\n';
}
int main()
{
foo();
return 0;
}