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

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// 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>
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#include <span>
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size_t getSize(double* ptr); // prototype
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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;
}
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int main() {
double numbers[20]; // 20 doubles; occupies 160 bytes on our system
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auto numbers_span {std::span<double>(numbers)};
fill_arr(numbers_span);
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std::cout << "Number of bytes in numbers is " << sizeof(numbers)<<"\n";
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std::cout << "Actual number of elements : " << sizeof(numbers)/sizeof(double) << "\n";
std::cout << "Number of bytes returned by getSize is " << getSize(numbers) << "\n";
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std::cout << "Actual number of elements returned by getSize_span is " << getSize_span(numbers) << "\n";
print_arr(numbers_span);
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}
// return size of ptr
size_t getSize(double* ptr) {
return sizeof(ptr);
}
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size_t getSize_span(std::span<double> ptr) {
return ptr.size();
}
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* *
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**************************************************************************/