fcn nBitAddr(as,bs){ //-->(carry, sn..s3,s2,s1,s0)
   (ss:=List()).append(
      [as.len()-1 .. 0,-1].reduce('wrap(c,n){
         c2,s:=fullBitAdder(c,as[n],bs[n]); ss + s; c2
      },0))
   .reverse();
}
println(nBitAddr(T(1,0,1,0), T(1,0,0,1)));