​​原文​​

import std.stdio;
import std.range;

auto next(Range)(Range r) {
    r.popFront;
    return r.front;
}
int main(string[] args) {
    auto i = iota(10);
    writeln(i.next);
    writeln(i.next);
    return 0;
}
//打印:

1
1

而

import std.stdio;
import std.range;

auto next(Range)(ref Range r) {
    r.popFront;
    return r.front;
}
int main(string[] args) {
    auto i = iota(10);
    writeln(i.next);
    writeln(i.next);
    return 0;
}
//打印
1
2