macro_rules! lower_bound {
(
$len:expr,
|$i:ident| $less_than:expr
) => {{
let mut i = 0usize;
let mut end: usize = $len;
while end > i {
let mid = i + (end - i) / 2;
let lt = {
let $i = mid;
$less_than
};
if lt {
i = mid + 1;
} else {
end = mid;
}
}
i
}};
}
#[cfg(test)]
mod tests {
use quickcheck_macros::quickcheck;
#[test]
fn const_lower_bound() {
const fn result() -> usize {
let array = [5, 5, 5, 5, 6, 6, 7, 8, 9, 10, 11, 12, 12, 12, 13, 13];
lower_bound!(array.len(), |i| array[i] < 12)
}
assert_eq!(result(), 11);
}
#[quickcheck]
fn lower_bound(mut values: Vec<u32>, arbitrary_value: u32) {
values.sort();
log::debug!("values = {:?}", values);
for (i, &e) in values.iter().enumerate() {
let mut expected = i;
while expected > 0 && values[expected - 1] == values[expected] {
expected -= 1;
}
let got = lower_bound!(values.len(), |i| values[i] < e);
log::debug!(
" lower_bound(values[{}]) = {} (expected {})",
i,
got,
expected
);
assert_eq!(got, expected);
}
for (i, win) in values.windows(2).enumerate() {
if win[1] - win[0] < 2 {
continue;
}
let mid = win[0] + (win[1] - win[0]) / 2;
let got = lower_bound!(values.len(), |i| values[i] < mid);
log::debug!(
" lower_bound(mean(values[{}] + values[{} + 1])) = {}",
i,
i,
got
);
assert_eq!(got, i + 1);
}
if values.is_empty() {
let got = lower_bound!(values.len(), |i| values[i] < arbitrary_value);
log::debug!(" lower_bound({}) = {}", arbitrary_value, got);
assert_eq!(got, 0);
} else {
if *values.first().unwrap() > 0 {
#[allow(unused_comparisons)]
let got = lower_bound!(values.len(), |i| values[i] < 0);
log::debug!(" lower_bound(0) = {}", got);
assert_eq!(got, 0);
}
if *values.last().unwrap() < u32::MAX {
let got = lower_bound!(values.len(), |i| values[i] < u32::MAX);
log::debug!(" lower_bound({}) = {}", u32::MAX, got);
assert_eq!(got, values.len());
}
}
}
}