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macro_rules! cartesian_impl {
($out:tt [] $b:tt $init_b:tt $submacro:tt) => {
$submacro!{$out}
};
($out:tt [$a:tt, $($at:tt)*] [] $init_b:tt $submacro:tt) => {
cartesian_impl!{$out [$($at)*] $init_b $init_b $submacro}
};
([$($out:tt)*] [$a:tt, $($at:tt)*] [$b:tt, $($bt:tt)*] $init_b:tt $submacro:tt) => {
cartesian_impl!{[$($out)* ($a, $b),] [$a, $($at)*] [$($bt)*] $init_b $submacro}
};
}
macro_rules! cartesian {
( $submacro:tt, [$($a:tt)*], [$($b:tt)*]) => {
cartesian_impl!{[] [$($a)*,] [$($b)*,] [$($b)*,] $submacro}
};
}
#[cfg(test)]
mod tests {
macro_rules! print_cartesian {
( [ $(($a1:tt, $a2:tt)),* , ] ) => {
fn test_f(x:i64, y:i64) -> Result<(i64, i64), ()> {
match (x, y) {
$(
($a1, $a2) => { Ok(($a1, $a2)) }
)*
_ => { Err(()) }
}
}
};
}
#[test]
fn print_cartesian() {
cartesian!(print_cartesian, [1, 2, 3], [4, 5, 6]);
assert_eq!(test_f(1, 4), Ok((1, 4)));
assert_eq!(test_f(1, 3), Err(()));
assert_eq!(test_f(3, 5), Ok((3, 5)));
}
}
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