SIMD mask

# `simd[bool, N]` is a type you can write (owner, 2026-09-27: a): a mask, one yes/no per
# lane, as a vector comparison gives. It has as many lanes as the vectors it compares, and
# `not`/`and`/`or` work lane by lane. A function can take one.
fn count_on ['m': simd[bool, 4]] -> bool {
    return simd.all['m'];
}
MAIN {
    let 'xs': array[int32] = [5, 20, 30, 40];
    let 'a': simd[int32, 4] = simd.load[lend 'xs', pos 1];
    let 'm': simd[bool, 4] = 'a' > simd.fill[value 10];
    let 'all': simd[bool, 4] = simd.fill[value true];
    let 'both' := 'm' and 'all';
    let 'flip' := not 'm';
    std::print.useful[simd.any['m'], " ", simd.all['m'], " ", count_on['both'], " ", simd.any['flip'], newln];
}