Proposal: Generator-based for loop
Proposal: Generator-based for loop
P2881 proposes a new way to build iterators, similar to generators but with less performance overhead and better nesting (and hence composability):
struct generator123
{
auto operator()(auto&& sink) const
{
std::control_flow flow;
// With P2561: sink(1)??;
flow = sink(1);
if (!flow) return flow;
// With P2561: sink(2)??;
flow = sink(2);
if (!flow) return flow;
return sink(3);
}
};
int main() {
for (int x : generator123()) // x iterates 1, 2, 3
{
std::print("{}\n", x);
if (x == 2)
break;
}
}
While the benefits are undisputable, it's quite verbose without P2561 and I feel C++ is starting to have too many different iterator models.
What do you think?
One of the authors has a nice presentation about pitfalls of ye olde for loops, which was probably a big motivator too: https://www.youtube.com/watch?v=95uT0RhMGwA
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