TEMPLATE halfadder {
  CELL <cellname> {
    CELLTYPE = block ;
    ATTRIBUTE { adder }
    PIN [<msb>:0] a_in {
      DIRECTION = input ;
    }
    PIN [<msb>:0] out {
      DIRECTION = output ;
    }
    FUNCTION {
      BEHAVIOR {
        out = a_in + c_in ;
      }
    }
    TEMPLATE carry_propagate {
      GROUP low_bits { 0 : <high_bit> }
      VECTOR ( ?! a_in[low_bits] -> ?! out[<high_bit>] ) {
        ENERGY = 1 ;
      }
    }
    GROUP high_bits { 0 : <msb> }
    carry_propagate = dynamic {
      high_bit = high_bits ;
    }
  }
}
halfadder {
  cellname = halfadder_8 ;
  msb = 7 ;
}