c-resources/CPlusPlus20ForProgrammers-master/examples/ch07/fig07_10.cpp

// fig07_10.cpp
// Sizeof operator when used on a built-in array's name
// returns the number of bytes in the built-in array.
#include <iostream>
#include <span>

size_t getSize(double* ptr); // prototype
size_t getSize_span(std::span<double> ptr);

void print_arr(auto a){
        for (auto x: a)
                std::cout << x << " ";
}

void fill_arr(auto& a){
        for (auto x: a)
                x = 0;
}


int main() {
   double numbers[20]; // 20 doubles; occupies 160 bytes on our system

   auto numbers_span {std::span<double>(numbers)};
   fill_arr(numbers_span);


   std::cout << "Number of bytes in numbers is " << sizeof(numbers)<<"\n";

   std::cout << "Actual number of elements : " << sizeof(numbers)/sizeof(double) << "\n";

   std::cout << "Number of bytes returned by getSize is " <<     getSize(numbers) << "\n";

   std::cout << "Actual number of elements returned by getSize_span is " <<     getSize_span(numbers) << "\n";

   print_arr(numbers_span);
}

// return size of ptr         
size_t getSize(double* ptr) {
   return sizeof(ptr);
}

size_t getSize_span(std::span<double> ptr) {
   return ptr.size();
}




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