MSVC supports for-each for 3 conditions:
1. C-style array: int arr[10]; for each (int &i in arr) {}
2. std::vector style iterators: vector<int> v; for each (int &i in v) {}
3. The most complex one, the one like in C#:
#include <iostream>
#define ARRAY_SIZE 3
int arr[ARRAY_SIZE] = { 1, 3, 5 };
struct Enumerator {
__declspec(property) int& Current;
int& GetCurrent() { return arr[index]; }
bool MoveNext() { index++; return index < ARRAY_SIZE; }
Enumerator() { index = -1; }
int index;
};
struct Collection {
Enumerator GetEnumerator() { return Enumerator(); }
};
int main() {
Collection c;
// Output: 1 \n 3 \n 5 \n
for each (int& i in c) {
std::cout << i << "\n";
}
}
The class that is "foreach"ed must have a method which returns a
enumerator class.
And this enumerator class must have a property named "Current" and a
"bool MoveNext()".
for each (T elem in collection) stmt
is translated to:
{
auto&& enumerator = collection.getEnumerator();
while (enumerator.MoveNext()) {
T elem = enumerator.Current; // Current is a property!!!
stmt
}
}
1. This patch only solves (3).
2. Enumerator class should have "Current" as a property, but for simplicity
I just translate to enumarator.GetCurrent(), instead of enumerator.Current
3. The logic is kind of mixed up with C++11 for-range loop. So there may be
some warnings like "for-range loop is C++11 extension", while we are using
foreach...
This patch is proved to behave correctly UNDER CORRENT CODE, and is used in
our product generation.
--
Best Regards, Tong Shen (沈彤)
1.patch
Description: Binary data
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