1. Scala HW5 Part 2 Combine Until Encode Decode

2. Combine Not sure what a correct test case is Fork(Leaf('d',4),Fork(Leaf('a',2),Leaf('b',3),List('a ', 'b'),5),List('d', 'a', 'b'),9)) val t2 = Fork(Fork(Leaf('a',2), Leaf('b',3), List('a','b'), 5), Leaf('d',4), List('a','b','d'), 9)

3. Combine function, not complete def combine1(trees: List[CodeTree]): List[CodeTree] = trees match{ case first::second::restofList => { val ct = makeCodeTree(first,second) //not correct, check weights and add to either front or back. Build test cases for both //how to insert in right place? can do a recursive traversal to insert //model after insertion sort code // if( weight(ct) < weight(restofList(0))) return ct::restofList // else // return (restofList++ct } case _ => trees //if less than 2 return trees }

4. def combine2(trees: List[CodeTree]): List[CodeTree] = { if (trees.length>=2) { val ct = makeCodeTree(trees(0),trees(1)) return ct::trees.drop(2) } else trees }

5. Until, currying, first called then second def until(singleton:List[CodeTree]=>Boolean, combiner:List[CodeTree]=>List[CodeTree])(zzz: List[CodeTree]):CodeTree = singleton(zzz) match{ case true =>/*println(zzz);*/zzz.head case false =>until(singleton,combiner)(combiner(zzz)) } Test case build tree: def createCodeTree(chars: List[Char]): CodeTree = { until(singleton,combine)(makeOrderedLeafList(times(chars))) }

6. Encode, do in steps Create 01s from tree, val tree=Fork(Leaf('a',2),Leaf('b',3),List('a', 'b'),5) Left is 0 right is 1. a=0,b=1 ab=01, step 1: loop through tree, no accumulator def encodeMe(tree:CodeTree,charList:List[Char]):Unit={ def encodeMeAcc(tree:CodeTree,testMe:Char,acc:List[Int]):Unit=tree match{ case Leaf(c:Char,w:Int) =>println("Leaf char:"+c+" weight:"+w); case Fork(left:CodeTree, right:CodeTree, charList:List[Char], weight:Int)=>{ println("Fork testMe:"+testMe+" chars(left):"+chars(left)+" chars(right):"+chars(right)) if(chars(left).contains(testMe)){ println(“left”) }else if(chars(right).contains(testMe)){ println("rigth!!! add 1 to list"); } // for(i<-charList){ // println("i:"+i) // encodeMeAcc(tree,i,List[Int]()); map doesnt work, key point in returning iterator, doesnt affect ctor charList.flatMap(x=>encodeMeAcc(tree,x,List[Int]())) }

7. Encode accumulator def encodeMe(tree:CodeTree,charList:List[Char]):List[Int]={ def encodeMeAcc(tree:CodeTree,testMe:Char,acc:List[Int]):List[Int]=tree match{ case Leaf(c:Char,w:Int) =>println("Leaf char:"+c+" weight:"+w);println("leaf acc:"+acc);acc case Fork(left:CodeTree, right:CodeTree, charList:List[Char], weight:Int)=>{ println("Fork testMe:"+testMe+" chars(left):"+chars(left)+" chars(right):"+chars(right)) if(chars(left).contains(testMe)){ println("left!!! add 0 to list"); val addMe = acc++List(0) println("addMe:"+addMe); encodeMeAcc(left,testMe,addMe) }else //if(chars(right).contains(testMe)){ println("rigth!!! add 1 to list"); val addMe = acc++List(1) println("addMe:"+addMe); encodeMeAcc(right,testMe,addMe) } for(i<-charList){ println("i:"+i) encodeMeAcc(tree,i,List[Int]()) }

8. Decode Nested pattern matching def decodeA(tree: CodeTree, bits: List[Bit]): Unit = { def decodeAcc(tree: CodeTree, bits: List[Bit]):Unit = tree match{ case Leaf(c:Char,w:Int) => println("leaf") case Fork(left:CodeTree, right:CodeTree, _,_ )=> bits match{ case Nil=>println("Nil list") case x::xs=>println("x:"+x+" xs:"+xs); decodeAcc(tree, xs) } decodeAcc(tree,bits) } println("decode") decodeA(Fork(Leaf('a',2),Leaf('b',3),List('a', 'b'),5),List(0,1,0,1,0,1))

9. Decode add acc def decodeB(ptree: CodeTree, bits: List[Bit]): List[Char] = { def decodeAcc(tree: CodeTree, bits: List[Bit],acc:List[Char]):List[Char] = tree match{ case Leaf(c:Char,w:Int) => println("leaf c:"+c+" acc:"+acc ); decodeAcc(ptree,bits,List(c)++acc) case Fork(left:CodeTree, right:CodeTree, list:List[Char], w:Int )=> bits match{ case Nil=>println("Nil"); acc case x::xs=>println("x:"+x+" xs:"+xs); if(x==0) { println("found 0 acc:"+acc) decodeAcc(left,xs,acc) } else{ println("found 1 acc:"+acc) decodeAcc(right,xs,acc) } decodeAcc(tree,bits,List[Char]()) } println("decode") val b = decodeB(Fork(Leaf('a',2),Leaf('b',3),List('a', 'b'),5),List(0,1,0,1,0,1)) println("b:"+b);