defproc inverter (bool? i; bool! o)
{
  prs {
    i => o-
  }
}

defproc nand2 (bool? a, b; bool! c)
{
  prs {
    a & b => c-
  }
}

defproc and2 (bool? a, b; bool! c)
{
  nand2 n(.a=a, .b=b);
  inverter i(.i=n.c, .o=c);  // note that we don't need the intermediate name _c
}