lambdaway :: powerset

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_h1 powerset

_ul [[https://rosettacode.org/wiki/Power_set|https://rosettacode.org/wiki/Power_set]]

{pre

'{def powerset

{def powerset.r
 {lambda {:ary :ps :i}
  {if {= :i {A.length :ary}}
   then :ps
   else {powerset.r :ary                 
                    {powerset.rr :ary :ps {A.length :ps} :i 0}
                    {+ :i 1}} }}}

{def powerset.rr
 {lambda {:ary :ps :len :i :j}
  {if {= :j :len}
   then :ps
   else {powerset.rr :ary 
                     {A.addlast! {A.concat {A.get :j :ps}
                                           {A.new {A.get :i :ary}}}
                                 :ps}
                     :len
                     :i 
                     {+ :j 1}} }}}

{lambda {:ary}
  {A.new {powerset.r :ary {A.new {A.new}} 0}}}}

-> {def powerset

{def powerset.rr
 {lambda {:ary :ps :len :i :j}
  {if {= :j :len}
   then :ps
   else {powerset.rr :ary 
                     {A.addlast! {A.concat {A.get :j :ps} {A.new {A.get :i :ary}}} :ps}
                     :len
                     :i 
                     {+ :j 1}} }}}

{lambda {:ary}
  {A.new {powerset.r :ary {A.new {A.new}} 0}}}}
}

_p testing

{prewrap
'{powerset {A.new 1 2 3 4}}
-> {powerset {A.new 1 2 3 4}}

'{powerset {A.new ø}}
-> {powerset {A.new ø}}
}

{script 
  var powerset_rr = function(ary,ps,len,i,j) {
    if (j === len)
      return ps
    else {
      ps.push( ps[j].concat(ary[i]) );
      return powerset_rr( ary, ps, len, i, j+1 );
    }
  };

var powerset_r = function(ary,ps,i) {
    if (i === ary.length)
      return ps 
    else
      return powerset_r( ary, powerset_rr(ary,ps,ps.length,i,0), i+1)
  };

var powerset = function(ary) {
  return powerset_r(ary,[ [] ],0)
};

var run = function() {
  var r = powerset([1,2,3,4]);
  document.getElementById("output").innerHTML = JSON.stringify(r)
};

setTimeout( run, 1 )
}