Update to C++-17
Updating to C++-17 allows us to use (list not complete):
- **Structured bindings:** A proposal for de-structuring initialization, that would allow writing `auto [ x, y, z ] = expr;` where the type of `expr` was a tuple-like object, whose elements would be bound to the variables `x`, `y`, and `z` (which this construct declares). Tuple-like objects include `std::tuple`, `std::pair`, `std::array`, and aggregate structures.
```cpp
using Coordinate = std::pair<int, int>;
Coordinate origin() {
return Coordinate{0, 0};
}
const auto [ x, y ] = origin();
x; // == 0
y; // == 0
```
```cpp
std::unordered_map<std::string, int> mapping {
{"a", 1},
{"b", 2},
{"c", 3}
};
// Destructure by reference.
for (const auto& [key, value] : mapping) {
// Do something with key and value
}
```
- **std::optional:** The class template `std::optional` manages an optional contained value, i.e. a value that may or may not be present. A common use case for optional is the return value of a function that may fail.
```cpp
std::optional<std::string> create(bool b) {
if (b) {
return "Godzilla";
} else {
return {};
}
}
create(false).value_or("empty"); // == "empty"
create(true).value(); // == "Godzilla"
// optional-returning factory functions are usable as conditions of while and if
if (auto str = create(true)) {
// ...
}
```
- **std::filesystem:** The new `std::filesystem` library provides a standard way to manipulate files, directories, and paths in a filesystem.
Here, a big file is copied to a temporary path if there is available space:
```cpp
const auto bigFilePath {"bigFileToCopy"};
if (std::filesystem::exists(bigFilePath)) {
const auto bigFileSize {std::filesystem::file_size(bigFilePath)};
std::filesystem::path tmpPath {"/tmp"};
if (std::filesystem::space(tmpPath).available > bigFileSize) {
std::filesystem::create_directory(tmpPath.append("example"));
std::filesystem::copy_file(bigFilePath, tmpPath.append("newFile"));
}
}
```
issue