Re: Integers and Mathematical Correctness

[James Rogers <jimmaureenrogers@worldnet.att.net>]

"Eric G. Miller" wrote:
> 
> #include <float.h>
> #include <limits.h>
> #include <math.h>
> 
> In C: sizeof float <= sizeof double <= sizeof long double
> 
> It's all there.  Granted, there are a few things where there's no analog
> in C that you'd have to code/check yourself (limited ranges, fixed
> precision).

The include files listed above declare constants for various values,
such as FLT_MAX. In one sense they are like 'First and 'Last in 
that they identify value boundaries. Unfortunately, these values in C
are not as useful as their Ada counterparts.

Take the following C snippet:

float f = FLT_MAX;
double d = 2;


f *= d;


What will the result of this be? There is no error issued either at
compile or run time. The value output by printf using a gcc
compiler is "1.#INF".

Note that C does a number of implicit conversions for the above code.
The integer 2 is implicitly converted to a double 2.0.
The calculation "f *= d" implicitly converts f to a double on the
right hand side, performs the calculation, then implicitly
converts the result back to a double.

Note that this error would have been caught by an Ada compiler.
C never notices the problem at all.

Jim Rogers
Colorado Springs, Colorado USA