Function unit

crates/kernel/src/whnf.rs:3536–3538

()

    let s = match args[0].data() {
      ExprData::Str(s, _, _) => s,
      _ => return Ok(None),
    };
    if is_utf8_byte_size {
      let n = Nat::from(s.len() as u64);
      let addr = Address::hash(&n.to_le_bytes());