The code example in this answer only works if you compile in C++17 mode - see how-to at the end of the answer
First, I recommend restructuring the data slightly. You have an output pin and an accociated millis time that you now store in separate arrays. I'd put them in a struct:
struct Output {
byte pin;
uint32_t ms;
};
You also need a container that can store objects and that has the begin() and end() member functions. I've put together an embryo, staticvector, which is sort of the worst of std::vector and std::array combined - but it's simple. The reason I didn't make it more like a std::array is that it should be able to store arrays of staticvectors of different sizes. The reason for not making it more like std::vector is because it requires a lot more code.
To make it easier to follow I've copied a few of the possible implementations of some standard templates from https://cppreference.com/ and put them in a namespace of their own. You can read about the templates on https://cppreference.com/ if they are unfamiliar.
namespace xyz {
template<class T> struct remove_reference {using type = T;};
template<class T> struct remove_reference<T&> {using type = T;};
template<class T> struct remove_reference<T&&> {using type = T;};
template<class T>
using remove_reference_t = typename remove_reference<T>::type;
template<class T>
constexpr T&& forward(remove_reference_t<T>& t) noexcept { return static_cast<T&&>(t); }
template<class T>
constexpr T&& forward(remove_reference_t<T>&& t) noexcept { return static_cast<T&&>(t); }
template<class T>
constexpr remove_reference_t<T>&& move(T&& t) noexcept {
return static_cast<remove_reference_t<T>&&>(t);
}
template<class T, class U = T>
constexpr T exchange(T& obj, U&& new_value) {
T old_value = move(obj);
obj = forward<U>(new_value);
return old_value;
}
} // namespace xyz
With those helper templates, the actual container could look like this:
template<class T>
class staticvector {
private:
size_t len = 0;
T* data = nullptr;
public:
// a constructor taking one or more T's and storing them in "data"
template<class U, class... V>
constexpr staticvector(U&& u, V&&... vs) :
len(sizeof...(V) + 1),
data{new T[sizeof...(V) + 1]{xyz::forward<U>(u), xyz::forward<V>(vs)...}}
{}
// copy constructor
staticvector(const staticvector& rhs) :
len(rhs.len),
data(new T[len])
{
auto rhs_it = rhs.data;
for(auto it = data, end = data + len; it != end; ++it, ++rhs_it) {
*it = *rhs_it;
}
}
// move constructor
staticvector(staticvector&& rhs) noexcept :
len(rhs.len), data(xyz::exchange(rhs.data, nullptr))
{}
// implement this if you wish
staticvector& operator=(const staticvector&) = delete; // copy assignment
// move assignment
staticvector& operator=(staticvector&& rhs) noexcept {
len = rhs.len;
// this could use `std::swap(data, rhs.data)`
auto *tmp = data;
data = rhs.data;
rhs.data = tmp;
}
~staticvector() { delete[] data; } // destructor
size_t size() const { return len; }
// subscript operator
const T& operator[](size_t idx) const { return data[idx]; }
T& operator[](size_t idx) { return data[idx]; }
// iterator support
using const_iterator = const T*;
using iterator = T*;
const_iterator cbegin() const { return data; }
const_iterator cend() const { return data + len; }
const_iterator begin() const { return cbegin(); }
const_iterator end() const { return cend(); }
iterator begin() { return data; }
iterator end() { return data + len; }
};
Now you can create a staticvector containing Output objects and also a container containing such containers.
using OutputGroup = staticvector<Output>; // a convenience alias
// All your arrays put into a container of containers
static const staticvector<OutputGroup> OUTPUTS{
OutputGroup{Output{4, 1000}},
OutputGroup{Output{5, 5000}, Output{6, 2000}, Output{7, 3000}}
};
void loop() {
// Two range-based for loops:
for (const OutputGroup& group : OUTPUTS) {
// structured bindings from each Output object in `group`
for (auto[pin, ms] : group) {
digitalWrite(pin, HIGH);
delay(ms);
digitalWrite(pin, LOW);
}
}
}
Demo
Using C++17 in Arduino projects
Current Arduino IDE uses g++ 7.3.0 and supports C++17 - but it's a bit messy to set it up.
- Find and edit
platform.txt - I found it in <installation_directory>/hardware/avr/1.8.3 but it may vary.
- Find the line that starts with
compiler.cpp.flags=
- Change
-std=gnu++11 to -std=gnu++17 on that line.
Important note: Programs using delete[] (like the above) will fail to link in C++17 mode because the arduino library doesn't include operator delete[](void* ptr, size_t), even in the Arduino IDE 2.0-beta.
The current workaround seems to be to add your own to the project:
void operator delete[](void* ptr, size_t) noexcept { free(ptr); }
With the above fixes, the above program compiled for Uno with these stats:
Sketch uses 2052 bytes (6%) of program storage space. Maximum is 32256 bytes.
Global variables use 43 bytes (2%) of dynamic memory, leaving 2005 bytes for local variables. Maximum is 2048 bytes.
