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Re: Bignumb addition function, suggestion improvements.

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Den lördag 14 mars 2015 kl. 14:41:35 UTC+1 skrev Ben Bacarisse:
> jonas.thornvall@gmail.com writes:
> 
> > I just wrote a big numb addition function this morning, it is a bit
> > silly and naive, not pure string not pure integer. I think it is
> > correct, but i may have missed leading last digit.
> 
> Yes, you do miss the leading digit in some cases.  And it's only for
> positive numbers.
> 
> > Suggestions to write it shorter and more clear, but keeping the naive
> > approach appreciated.
> >
> > <SCRIPT LANGUAGE="Javascript">
> >
> > function naiveAdd(strOne,strTwo) {
> > if (strOne.length>=strTwo.length) {length=strOne.length;} else {length=strTwo.length;}
> > oneS = strOne.split("").reverse().join("");
> > twoS = strTwo.split("").reverse().join("");
> 
> I would avoid this reversing operation.  It's not needed since you can
> get the charCodeAt any index value you like.
> 
> > out="";
> > remainder=0;
> 
> Use var.
> 
> > for (i=0;i<length;i++){
> >          one=oneS.charAt(i);
> >          two=twoS.charAt(i);
> >          one=parseInt(one);
> >          two=parseInt(two);
> >          if (isNaN(one)) one = 0;
> >          if (isNaN(two)) two = 0;
> >          sum=one+two+remainder;
> >          if (sum>=10) { sum=sum-10; remainder=1;} else {remainder=0;}
> >          out=sum+out;
> >     }
> 
> There's a bit of duplication here and a bug: you forget that the carry
> (the usual name for your 'remainder') can be set at the end of the loop.
> 
> > document.write("Sum = ",out,"<BR>");
> > }
> >
> > strOne="9003";
> > strTwo="13039";
> > naiveAdd(strOne,strTwo);
> >
> > </SCRIPT>
> 
> String.prototype.digitValueAt = function (pos) {
>     var d = this.charCodeAt(pos);
>     return isNaN(d) ? 0 : d - 48;
> }
> 
> function naiveAddX(strOne, strTwo) {
>     var i1 = strOne.length, i2 = strTwo.length, result = "", carry = 0;
>     while (i1 > 0 || i2 > 0 || carry > 0) {
>         var dsum = strOne.digitValueAt(--i1) + strTwo.digitValueAt(--i2) + carry;
>         if (dsum >= 10) {
>             dsum -= 10;
>             carry = 1;
>         }
>         else carry = 0;
>         result = dsum + result;
>     }
>     return result;
> }
> 
> You could also build a result array and create the string on one go.
> That's probably faster.
> 
> -- 
> Ben.

I felt something was wrong but the result seemed to come out correct but i did not try strings of equal length with carry at first digit.

I did need to add a digit if carry was 1 after loop.

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Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-14 04:15 -0700
  Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-14 04:40 -0700
    Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-14 04:56 -0700
  Re: Bignumb addition function, suggestion improvements. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-14 13:41 +0000
    Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-14 10:17 -0700
      Re: Bignumb addition function, suggestion improvements. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-14 19:39 +0000
        Re: Bignumb addition function, suggestion improvements. Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-03-14 20:56 +0100
        Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 01:52 -0700
          Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 02:57 -0700
            Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 03:07 -0700
    Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-14 10:57 -0700
    Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 03:40 -0700
      Re: Bignumb addition function, suggestion improvements. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-15 11:06 +0000
      Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 04:09 -0700
  Re: Bignumb addition function, suggestion improvements. Dr.Kral@nyc.rr.com - 2015-03-14 19:51 -0400
    Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-14 23:57 -0700
    Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 00:08 -0700
  Re: Bignumb addition function, suggestion improvements. John Harris <niam@jghnorth.org.uk.invalid> - 2015-03-15 10:46 +0000
    Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 04:12 -0700
      Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 06:00 -0700
    Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 04:27 -0700
      Re: Bignumb addition function, suggestion improvements. jonas.thornvall@gmail.com - 2015-03-15 05:30 -0700

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