On Sat, Oct 10, 2009 at 7:14 PM, David Emerson <dle...@angelbase.com> wrote: > 1. Is there a way to get the highest and lowest real values? I can do > high(longint) but high(real) gives me an error. Also of interest is a > low(real) value (-m * 10^n) as distinct from the smallest real value > (m * 10^-n)
As stated in the Documentation: http://www.freepascal.org/docs-html/ref/refsu6.html The Real Type is Plattform dependend and either Single or Double. And since its IEEE Floating Point Representation, Low = -High (just a difference in sign bit) You can find Max/Min Single/Double in unit math. Sample: -- uses math; ... WriteLn( 'Size: ', SizeOf(Real) ); if SizeOf(Real)>=8 then begin WriteLn( 'Low: ', -MaxDouble ); WriteLn( 'High: ', MaxDouble ); end else begin WriteLn( 'Low: ', -MaxSingle ); WriteLn( 'High: ', MaxSingle ); end; -- > 2. For the purposes of reserving memory in block sizes that can be > easily reallocated, I like to use powers of two. So if I have, e.g., a > dynamic array, I might start with a size of 1024 and then double it > when it hits capacity. Hopefully this smoothes memory management, as I > am using a lot of memory... > > Anyway, what I'd like is a simple function that can quickly identify the > next power-of-two larger than an arbitrary number. So if I feed the > function 472, it will return 512. Thus far I haven't been able to > figure out how to do this without a big if-then-else nest. Is there > some clever way to request that the processor return the position of > the leftmost '1' in 00101101? invalue := 412; -- outvalue := 1; while invalue <> 0 do begin invalue := invalue div 2; outvalue := outvalue*2; end; -- BUT.. this "allocation algorithm" may be good in theory (amortized performance for reallocation), but youre losing a lot of memory because of prereservation.. just for the records ;) regards, Matthias _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
