Really Simple Math

  • Thread starter Thread starter Christopher Weaver
  • Start date Start date
C

Christopher Weaver

I've declared o to be a double and c an int. No matter what the value of c,
o is never greater than 0 after the following line of code:

o = (c / 100);


Any ideas why?
 
I've declared o to be a double and c an int. No matter what the value
of c, o is never greater than 0 after the following line of code:

o = (c / 100);


Any ideas why?
Click to expand...
c/100 performs integer division. If c is less than 100 then c/100 will
be a 0. If you want the value you expect, use

o = c / 100.0 now you do floating point division.
Any introductory programming book will go over this.

(BTW, o is a poor name of a variable of 1 character length.)


--
Dennis Roark

(e-mail address removed)
Starting Points:
http://sio.midco.net/denro/www
 
Thanks. I knew it was basic. In fact, as I read your reply I recalled the
point being made in my first semester c++ class. Years of Pascal has erased
much of that.

BTW, the 'o' was included for debugging purposes only.
 
Christopher said:
I've declared o to be a double and c an int. No matter what the value of c,
o is never greater than 0 after the following line of code:

o = (c / 100);


Any ideas why?
Click to expand...
No idea IF your claim is correct. However, I think what you really mean is "No
matter what the value of c (as long as it's less than 100), o is never greater
than 0."

The expression (c / 100) is apparently calculated using integer arithmetic,
which is perfectly reasonable since c and 100 are both integer expressions. The
integer result of this division will be zero when c is less than 100. I suggest
you test your "no matter what" claim with some larger values of c (e.g., 100,
101, 199, 200, 201, 299, etc.) and watch what happens.

-rick-
 
Good point. It's so nice to have a group that pays attention and cares
enough to write.
 
Altramagnus said:
Personally I prefer to use:

o = c * 0.01;

Is it faster?
Perharps negligible.
Click to expand...

I don't think it's nearly as clear at a glance that that's dividing by
a hundred though. Just MHO.
 
Altramagnus said:
i agree, but you can put a comment or something.
Click to expand...

If you have to put a comment on one version to make it clearer, and you
haven't proved it to be faster, why do you prefer it? I'd take
readability over unproven speed any day.
 
Back
Top