fn f(x:u1, y:u8, z:u16) = {
  {a,b:u1}:tup{u1,u1} = tup{x,1}
  def {yc, ...c, yc==y & match{tuplen{c},3}} = tup{y,b,y,b,y}
  {...d,e,f,g} := c
  emit{u32,'all',a,f,g}
}