Further investigation reveals that
(def b (byte i))
is doing something equivalent to this internally:
byte b = Byte.parseByte(String.format("%d",i));
which does indeed throw a NumberFormatException if the decimal integer
representation given to it produces an out-of-range value (as it
should).
So - what I'm pleading for, is that (byte b) and (int i), (short s),
etc. should simply perform a masking operation (on the appropriate
number of least significant bits) in the way that java clearly does.
On Feb 12, 1:08 pm, timc <[email protected]> wrote:
> Sorry I did not make myself clear - I thought it was obvious given the
> previous postings on this subject.
> This java program:
>
> public class TestByte {
> public static void main(String[] args)
> {
> int i = 0x123456ab;
> byte[] b = new byte[1];
> b[0] = (byte) i;
> showInt("i",i);
> showByte("b[0]",b[0]);
> }
>
> private static void showInt(String s, int x)
> {
> System.out.println(String.format("%s=%d(0x%08x 0x%02x)", s,
> x, x,
> x));
> }
>
> private static void showByte(String s, byte x)
> {
> System.out.println(String.format("%s=%d(0x%08x 0x%02x)", s,
> x, x,
> x));
> }
>
> }
>
> compiles and runs, producing this output:
>
> i=305419947(0x123456ab 0x123456ab)
> b[0]=-85(0x000000ab 0xab)
>
> But, this bit of clojure:
>
> (defn show [s x] (println (format "%s=%d(0x%08x 0x%02x)" s, x, x, x)))
> (def i 0x123456ab)
> (def b (byte-array 1))
> (aset-byte b 0 (byte i))
> (show "i" i)
> (show "b[0]" (aget b 0))
>
> throws this exception:
> java.lang.IllegalArgumentException: Value out of range for byte:
> 305419947
>
> Shouldn't these two programs be equivalent?
> Presumably they are not because the effect of
>
> int i = (byte) b;
>
> is NOT the same as
>
> (def i (byte b))
>
> -- but surely it should be the same?
>
> On Feb 11, 5:24 pm, Andy Fingerhut <[email protected]> wrote:
>
> > What can you not do with the signed byte type and arrays of bytes
> > (Java byte[] and Clojure (byte-array ...))?
>
> > I believe these are frequently used for Java I/O, and can be used for
> > Clojure I/O as well.
>
> > Andy
>
> > On Feb 11, 2011, at 9:22 AM, timc wrote:
>
> > > How on earth is one supposed to do communication programming (not to
> > > mention handling binary files etc) without an unsigned byte type?
>
> > > I see that this issue has been talked about vaguely - is there a
> > > solution?
>
> > > Thanks
>
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