function-refactor.js

// https://github.com/Mariana88/binary-addition

// her code for binary addition
// it's so long since she constrained herself to using only strings
// this makes binaryStrAddition long, 
//    she had to do logical comparisons between strings
//    rather than simply pulling out elements
// it doesn't work with negative numbers, but that's not important for this execise

// we looked at how she split her primary strategy (binaryAddition) into two sub-procedures

// then we analyzed her strategy in convertToBinaryStr
//    first while loop finds how many digits in the binary representaion (highest power)
//    second loop builds up the binary representation
// as a little experiment we split this function into two functions
//    one for each step in the above strategy
// we decided this was not a useful modularization 
//    converting to binary is probably more useful as a procedure in the future
//    and both sub-tasks are not

function convertToBinaryStr (num){
    let hP = 0;
    let numStr = '';
    let workNum;
    if (num>=0){
        workNum = num;
    } else {
        workNum = -(num);
    }
    while (workNum - Math.pow(2, hP) >= 0){
        hP++;
    }
    hP--;
    while (hP>=0){
        if (workNum - Math.pow(2, hP) >=0){
        numStr = numStr + 1;
        workNum = workNum - Math.pow(2, hP);
        } else {
        numStr = numStr + 0;
        }
        hP--;
    }
    if (num <0){
        numStr = "-" + numStr;
    }
    return numStr;
}

function binaryStrAddition (binaryStr1, binaryStr2){
    let addedBinary = "";
    let extra = 0;
    let i= binaryStr1.length - 1;
    let j= binaryStr2.length -1;
    while (i>=0 || j>=0){
        if ((binaryStr1[i] == 0 || binaryStr1[i] == undefined) && (binaryStr2[j]==0 || binaryStr2[j] == undefined) && extra==0){
            addedBinary = 0 + addedBinary;
            extra = 0;
        } else if ((((binaryStr1[i] == 1 && (binaryStr2[j]==0 || binaryStr2[j]==undefined))|| 
                    ((binaryStr1[i] == 0 || binaryStr1[i]==undefined) && binaryStr2[j]==1)) && extra == 0) ||
                    ((binaryStr1[i]==0 || binaryStr1[i]==undefined) && (binaryStr2[j]==0 || binaryStr2[j]==undefined) && extra==1)){
            addedBinary = 1 + addedBinary;
            extra =0;
        } else if (binaryStr1[i] == 1 && binaryStr2[j]==1 && extra == 1){
            addedBinary = 1 + addedBinary;
            extra = 1;
        } else {
            addedBinary = 0 + addedBinary;
            extra = 1;
        }
        i--;
        j--;
    }
    if (extra == 1){
        addedBinary = 1 + addedBinary;
    }
    return addedBinary;
}


function binaryAddition (num1, num2){

    let myBinaryStr1 = convertToBinaryStr(num1);
    let myBinaryStr2 = convertToBinaryStr(num2);
    return binaryStrAddition (myBinaryStr1, myBinaryStr2);
}