[fpc-devel] Floating point precision

[Jonas Maebe]

On 06 Apr 2007, at 21:36, Colin Western wrote:

> Can I ask what determines the precision of floating point  
> calculations are done in? It seems that fpc treats (for example,  
> with J declared as integer)
>
> 1/sqrt(J+1.0) as single
>
> but
>
> 1/sqrt(J+1) as double

In 2.1.2 and 2.2, both will be evaluated as single (except on 80x87,  
because it is not possible to tell the 80x87 to perform a particular  
calculation using only single/double precision).

> which seems counter-intuitive. In FORTRAN I can force double  
> precision evaluation with sqrt(J+1.0D0) but there is no equivalent  
> idea of a double constant in Pascal.

The Pascal equivalent is sqrt(j+double(1.0)).


Jonas