Basic Math Error

Summary:

error with an answer in math section

Basic Math Error

Sorthious (guest) 29 Jan 2013 17:05

Under Compound Assignment Operators

int b = 7;
...
b *= 5 // This is the same as b = b * 5; At this point b would be 20.

b should be 35

Sorthious (guest) 29 Jan 2013 17:08

Oh…and thank you, by the way, for this tutorial. It's put together really well and doesn't make the mistake most tutorials make by being too dry.

Sorthious (^8

rbwhitaker 29 Jan 2013 19:16

Hi Sorthious, thanks for the feedback! I'm glad you're finding it useful.

Are you talking about near the end of this tutorial?

If so, I think the numbers are actually correct, at least when you go through all of the code sequentially (as opposed to considering each line individually). That's what I was presuming to do, but perhaps I didn't make that clear enough in my tutorial.

Here's that whole block again:

int b = 7;
b -= 3; // This is the same as b = b - 3;  At this point b would be 4.
b *= 5; // This is the same as b = b * 5; At this point b would be 20.
b /= 4; // This is the same as b = b / 4;  At this point b would be 5.
b %= 2; // This is the same as b = b % 2;  At this point b would be 1.

On the first line, b starts out being 7.

On the second line, 3 is subtracted from b, resulting in a value of 4, and that is stored back into b. So at the end of running the second line, b contains a value of 4.

On the third line (the one in question) b starts with a value of 4 and is multiplied by 5 to get 20. This is then put back into b. So after running line #3, b should contain a value of 20, as the comment suggests.

And so on through the rest of the code.

You're right, if we were just looking at the original starting value of 7, and then ran just the multiplication line (without the subtraction line in between) we'd have a value of 35 instead.

The other thing is, after you pointed this block of code out to me, I saw that I was missing some semicolons. I've got those fixed now, thanks to you!

Thanks again for bringing this up, and if you see anything else that looks like it might be out of place, don't hesitate to let me know!

Sorthious (guest) 29 Jan 2013 20:20

Yeah…you nailed it….I was taking each line as an individual example of a Compound Operator…haha