> > > > Oooohhhh, I don't know about that.  The NetBSD/vax port uses native VAX
> > > > floating point operations, and they're not IEEE compliant.  They're VAX
> > > > D_float format.   There's the odd problem here and there, but it doesn't
> > > > wreak great havoc.
> > > 
> > > But it's always been that way on the Vax (IIRC Vax FP predates IEEE).  On 
> > > the ARM, it has always been IEEE, so to change would break compatibility.
> > 
> > It would ONLY break float compatibility. Floats are mostly used just
> > inside programs, not for communication with other programs. Usually
> > reals are stored as ASCII numbers in text files, not as IEEE numbers.
> > 
> > Besides, as i suggested only changing the format of floats, not doubles,
> > IEEE format would also be available. In C numbers are by default passed
> > as doubles anyway.
> 
> Not for ANSI in the presence of a prototype that declares the parameter as 
> float.

Of course. In that case it would of course be passed as a float, 
which is the whole point. Use float for faster math.

> > The whole point of the endeavour was to have the
> > possibility of accelerating math about tenfold for simple operations
> > of lesser accuracy when needed, such as in 3d programming, numerical
> > simulations, etc. 
> > 
> > Kim0
> 
> 
> And as I said, any program that had 
> 
>   float f;
> 
>    ...
> 
>   if ( f < (float)0.5 )
>     ...
> 
> 
> would now fail if it were compiled before your change because the binary 
> representation is now different.
> 
> The (trivial) program below illustrates this.
> 
> int x (float a)
> {
>   float b = a * (float)3.0;
> 
>   if (b < (float)0.5)
>     return 1;
>   return 0;
> }
> 
> Which compiles to:
> 
> _x:
>         mov     ip, sp
>         stmfd   sp!, {fp, ip, lr, pc}
>         ldr     r1, L5  @ float
>         sub     fp, ip, #4
>         bl      ___mulsf3
>         ldr     r1, L5+4        @ float
>         bl      ___ltsf2
>         mov     r0, r0, lsr #31
>         ldmea   fp, {fp, sp, pc}
> L6:
>         .align  0
> L5:
>         .word 0x40400000        @ float 3.00000000000000000000e0
>         .word 0x3f000000        @ float 5.00000000000000000000e-1
> 
> This is *user* code and calls *library* functions.  If the two differ over 
> the format then the results will be garbage.

Sigh. GCC is able to get the right library. At least VAX and Sparc gcc
does it right.

Why do you come with simple programming exercises as if they were
great obstacles?

Kim0