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Programming-Idioms

# 319 Generator function
Write a function g that behaves like an iterator.
Explain if it can be used directly in a for loop.
New implementation

Be concise.

Be useful.

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Please do not paste any copyright violating material.

Please try to avoid dependencies to third-party libraries and frameworks.

Other implementations 
List<int> g(int start) sync* {
  while (true) {
    yield start;
    start++;
  }
}
func generator() chan int {
	ch := make(chan int, 16)
	go func() {
		defer close(ch)
		timeout := time.After(2 * time.Minute)
		
		for i := 0; i < 1024; i++ {
			select {
			case ch <- i:
			case <-timeout:
				return
			}
		}
	}()
	return ch
}
import static java.util.stream.Stream.generate;
import java.util.Random;
import java.util.function.Supplier;
import java.util.stream.Stream;
Random r = new Random();
Supplier<Integer> s = r::nextInt;
Stream<Integer> g = generate(s);
import static java.util.stream.Stream.iterate;
import java.util.stream.Stream;
Stream<?> g = iterate(0, i -> i + 1).limit(100);
sub _upto (&) { return $_[0]; }  # prototype & is for a function param
sub upto {
    my ($start, $end) = @_;

    my $n = $start;

    return _upto {
        return
            wantarray ? $start .. $end    :
            $n > $end ? ($n = $start, ()) :
            $n++
            ;
        };
}
my $it = upto(3, 5);
foreach ( $it->() ) { print ' ' . $_ }

def g():
    for i in range(6):
        yield i
g = (1..6).each

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