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Re: Computed values don't tie up

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On 04/03/2012 03:29 PM, rkfb wrote:
> I'm reading 'C Programming: A Modern Approach' by KN King.
> 
> If I run celcius.c (as below) and enter a value of 32 (or 32.0) I am given 
> the equivalent celcius temperature as -2.2. Surely it should be zero?
> 
> /* Converts a Fahrenheit temperature to Celcius */
> 
> #include <stdio.h>
> 
> #define FREEZING_PT 32.0f
> #define SCALE_FACTOR (5.0f / 9.0f)
> 
> int main(void)
> {
>  	float fahrenheit, celcius;
> 
>  	printf("Enter Fahrenheit temperatue: ");
>  	scanf("%f", &fahrenheit);

Like most I/O functions, scanf() can fail. You should always check to
see whether or not it did fail. If so, there's no guarantee that
'fahrenheit' contains a representation of a valid floating point value;
it could contain a signaling NaN, for instance, so you should only
execute the rest of your program is scanf() succeeded.

>  	celcius = (fahrenheit - FREEZING_PT) * SCALE_FACTOR;
> 
>  	printf("Celcius equivalent: ".1f", celcius);

This line has one too many double quote characters; your code as
presented here should not have compiled without diagnostics, so this
can't be your actual program. Please cut and paste the actual text of
your program; that will make it much easier to figure out what's going
wrong.
Also, if the output from your program does not end with a new-line
character, the behavior is undefined; on many systems that's not a
problem, but even where it is permitted, I think it would be better to
append a '\n' to the printf() format string.

When I correct the issues I've raised above in the obvious ways, and
type in 32, it prints out 0; so that's another reason to think that this
in not exactly your actual program.

>  	return 0;
> }

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Computed values don't tie up rkfb <rkfb@rebelCode.slacknet> - 2012-04-03 19:29 +0000
  Re: Computed values don't tie up James Kuyper <jameskuyper@verizon.net> - 2012-04-03 14:57 -0400
    Re: Computed values don't tie up Robert <rkfb1965@googlemail.com> - 2012-04-03 21:37 +0000
      Re: Computed values don't tie up Robert <rkfb1965@googlemail.com> - 2012-04-03 21:39 +0000
      Re: Computed values don't tie up Ike Naar <ike@iceland.freeshell.org> - 2012-04-03 20:52 +0000
        Re: Computed values don't tie up James Kuyper <jameskuyper@verizon.net> - 2012-04-03 16:56 -0400
          Re: Computed values don't tie up "BartC" <bc@freeuk.com> - 2012-04-03 22:11 +0100
      Re: Computed values don't tie up "BartC" <bc@freeuk.com> - 2012-04-03 21:53 +0100
        Re: Computed values don't tie up Robert <rkfb1965@googlemail.com> - 2012-04-03 22:56 +0000
      Re: Computed values don't tie up Geoff <geoff@invalid.invalid> - 2012-04-03 20:05 -0700
      Re: Computed values don't tie up Martin Ambuhl <mambuhl@earthlink.net> - 2012-04-04 00:38 -0400
  Re: Computed values don't tie up "BartC" <bc@freeuk.com> - 2012-04-03 21:04 +0100
    Re: Computed values don't tie up Robert <rkfb1965@googlemail.com> - 2012-04-03 21:38 +0000
  Re: Computed values don't tie up Kleuske <kleuske@nowhere.net> - 2012-04-03 23:09 +0000
    Re: Computed values don't tie up Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-04-04 04:42 +0100

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