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Re: Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi]

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In article m25kdv$tou$1@dont-email.me, Eric Sosman said...

> On 10/21/2014 5:22 AM, ĵess stone wrote:
>>
>> Well, this *is* the language whose designers had the absolutely
>> *brilliant* idea of making the only byte-sized data type signed. And
>> prone to being auto-promoted to int.
> 
>      I'll agree that making `byte' signed was a regrettable choice,
> but what do you find repugnant about promoting it to `int'?  (And do you
> have a similar objection to promoting `short'?)

The problem is mainly the interaction with that and the signedness of 
bytes. So you end up with binary 11001001 turning into 
10000000000000000000000001001001 and when you later truncate or mask off 
the high bytes you wind up with 01001001, which is wrong. So you have to 
watch that you don't lose the high bit when something causes auto-
promotion. And it's tricky, because it can happen even if you have a 
computation "entirely in bytes", i.e. nothing but bytes in and assignment 
to a parameter or local of byte size. Java may still turn some of the 
intermediate calculations silently into ints, when it seems that work 
with bytes into bytes ought to not do that.

Ultimately, this stems from treating bytes mainly as really small 
integers, assuming you'll mainly use them to do arithmetic with wider 
types and will want wide output, when in reality bytes are mainly used 
for fiddling with binary data at a low level.

Preferable would have been a byte type that required explicit casts to 
widen, and which of course was unsigned. In theory it could still be 
added, by adding a "ubyte" type or similar (breaking source compatibility 
with older Javas by adding a new reserved word, though) with unsigned 
semantics and no auto-promotion to wider types -- only explicit casts or 
direct assignment to a wider type would widen it. For easy interoperation 
with legacy code it should be assignable to the existing byte type 
without the binary being changed (meaning that, numerically, 255 would 
turn into -1 when such an assignment was performed).

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Driving 7-Segment LEDs on Raspberry Pi javalaurence@gmail.com - 2014-10-20 01:28 -0700
  Re: Driving 7-Segment LEDs on Raspberry Pi Gordon Levi <gordon@address.invalid> - 2014-10-21 01:42 +1100
    Re: Driving 7-Segment LEDs on Raspberry Pi javalaurence@gmail.com - 2014-10-24 05:20 -0700
      Re: Driving 7-Segment LEDs on Raspberry Pi Arne Vajhøj <arne@vajhoej.dk> - 2014-10-24 21:37 -0400
  Re: Driving 7-Segment LEDs on Raspberry Pi ĵess stone <j3ss.st0n3@gmail.com> - 2014-10-20 17:16 +0000
    Re: Driving 7-Segment LEDs on Raspberry Pi javalaurence@gmail.com - 2014-10-21 00:09 -0700
      Re: Driving 7-Segment LEDs on Raspberry Pi ĵess stone <j3ss.st0n3@gmail.com> - 2014-10-21 09:22 +0000
        Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi] Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-10-21 08:43 -0400
          Re: Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi] ĵess stone <j3ss.st0n3@gmail.com> - 2014-10-22 06:42 +0000
            Re: Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi] Andreas Leitgeb <avl@auth.logic.tuwien.ac.at> - 2014-10-22 08:02 +0000
              Re: Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi] ĵess stone <j3ss.st0n3@gmail.com> - 2014-10-22 10:49 +0000
            Re: Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi] Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-10-22 08:52 -0400
              Re: Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi] ĵess stone <j3ss.st0n3@gmail.com> - 2014-10-22 14:00 +0000
                Re: Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi] Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-10-22 10:43 -0400
                Re: Bytes [Was: Re: Driving 7-Segment LEDs on Raspberry Pi] thinbluernime <thinbluernime3@gmail.com> - 2014-10-22 16:34 +0000

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