for.singeli

local {
  include 'skin/cop'
  def ux = primtype{'u', width{*void}}
  def num{n} = is{'number',kind{n}}
  def loop_var{a, b} = {
    if (num{a}) { cast{if (num{b}) ux else type{b}, a} }
    else {
      def ta=type{a}
      match (b) { {_:tb if ta<tb}=>promote{tb,a}; {_}=>a }
    }
  }
}

def for{vars,begin,end,iter} = {
  i := loop_var{begin, end}
  while (i < end) {
    iter{i, vars}
    i = i + 1
  }
}

def for_backwards{vars,begin,end,iter} = {
  i := loop_var{end, begin}
  while (i > begin) {
    i = i - 1
    iter{i, vars}
  }
}

def for_const{vars,begin,end,iter if num{begin} and num{end}} = {
  each{iter{., vars}, begin + range{end-begin}}
}

def for_unroll{unr if num{unr}}{vars,begin,end,iter} = {
  i := loop_var{begin, end}
  while (i + unr <= end) {
    each{{j}=>iter{i+j, vars}, range{unr}}
    i = i + unr
  }
  while (i < end) {
    iter{i, vars}
    i = i + 1
  }
}