Re: Re: Initialization and Floating Problem.

Kedar,

The difference in behavior of ANSI C floating point
constants and traditional C floating point constants
can cause numerical and perfomance differences in Code
ported from traditional C to ANSI C compiler.

Consider the following example:

#define PI 3.1415926
float a, b;

b = a * PI;

The result type of b depends on which compilation
options you use.

Table 2.1 Shows effect of compilation options on
floating point conversions.

Compilation   PI Constant Type    Behavior
Option
-cckr        double             (float)((double)a*PI)
-cckr -float float              a * PI
-xansi       double             (float)((double)a*PI)
-ansi        double             (float)((double)a*PI)

Each conversion incurs computational overhead.

The -float flag has no effect if you also specify
-ansi or -xansi. To prevent the promotion of floating
constants to double(and promoting the computation to a
double precision multiply) you must specify the
constant as a single precision floating point
constant. In the previous example, you would use the
following statement.

#define PI 3.1415926F   /* Single Precision float */

Traditional C(compiled with the -cckr option) does
noot recognized the float qualifier, f, however,
instead, write the constant definition as follows:

#ifdef __STDC__
#define PI 3.1415926f
#else
#define PI 3.1415926
#endif

-alain
JairoSoft Team


--- kedarpathikonda <[email protected]> wrote:

> 2.
> > float c=0.7;
> > if(c<0.7)
> > printf("yes");
> > else
> > printf("no");
> >
> > output:-yes
> > if i write c<0.7f then it
> > prints no.
> > i would like to know the reason
> > behind this i.e
> > what's happening internally.
> 
> 
> 
> the reason is because if give if(c<0.7) it will take
> 0.7 as double by 
> default
> 
> 
> 



		
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