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digitalmars.D.bugs - [Issue 3850] New: Signed/unsigned bytes type name

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=3850

           Summary: Signed/unsigned bytes type name
           Product: D
           Version: 2.040
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



While programming in D I have seen that you can forget that the "byte" is
signed. (Because normally I think of bytes as unsigned entities. Other people
share the same idea). (It's similar but not equal to the situation of signed
and unsigned chars in C).

There are several ways to solve this small problem. One of the simpler ways I
can think of is to deprecate the "byte" type name and introduce a "sbyte" type
name (that replaces the "byte" type name). Using a sbyte it's probably quite
more easy to not forget that it's a signed value.

This introduces an inconstancy in the naming scheme of D integral values (they
are now symmetric, ubyte, byte, int, uint, etc), but it can help avoid some
bugs, especially from D newbies.

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Feb 24 2010
next sibling parent d-bugmail puremagic.com writes:
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- The sbyte type represents signed 8-bit integers with values between -128 and
127.
- The byte type represents unsigned 8-bit integers with values between 0 and
255.

Choosing ubyte/sbyte is acceptable too.

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Mar 14 2010
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Andrej Mitrovic <andrej.mitrovich gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |andrej.mitrovich gmail.com



19:52:53 PDT ---
Although I agree with you I think it's way too late to fix this without
breaking tons of code. You can always use an alias in your own code. Adding it
to Phobos would probably be unwise too (people would ask what's the difference
between byte and sbyte).

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Oct 21 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
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                 CC|                            |clugdbug yahoo.com.au



This is not a newbie issue. I make this mistake myself, fairly often. *Walter*
made this mistake once, in the header generation tool! My experience is that
90% of uses of "byte", should instead be "ubyte". It is really, really unusual
to be using signed bytes.

I wish we could change this. (I would do it by changing the type to "sbyte" and
then adding "alias byte = sbyte;" to object.d).

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Oct 22 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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08:58:02 PDT ---


 This is not a newbie issue. I make this mistake myself, fairly often.


Absolutely, it happens to me all the time as well.


 I wish we could change this. (I would do it by changing the type to "sbyte" and
 then adding "alias byte = sbyte;" to object.d).


That still won't prevent you from making the mistake of typing 'byte' instead
of 'ubyte' though. :)

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Oct 22 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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 That still won't prevent you from making the mistake of typing 'byte' instead
 of 'ubyte' though. :)


If you have sbyte and ubyte, and you keep using them consistently, I think this
alone helps reduce mistakes a little.

And once few years have passed, and using "byte" is considered a bad idiom, D
programs in the wild use "byte" less and less, we can even consider deprecating
it.

There are tons of C++ code that represents null as "0", yet in C++11 there is
nullptr, and G++ from version 4.7 has a warning
(-Wzero-as-null-pointer-constant) that allows to find usage of "0" to represent
null pointer.

The most important thing is the desire to improve the situation, then some slow
deprecation paths exist.

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Oct 22 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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 I wish we could change this. (I would do it by changing the type to "sbyte"
 and then adding "alias byte = sbyte;" to object.d).





 That still won't prevent you from making the mistake of typing 'byte' instead
 of 'ubyte' though. :)


By itself, no, but anybody can modify their local copy of object.d to remove
the alias...
A very slow deprecation path is possible.

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Oct 23 2012
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Daniel Kozak <kozzi11 gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kozzi11 gmail.com





 While programming in D I have seen that you can forget that the "byte" is
 signed. (Because normally I think of bytes as unsigned entities. Other people
 share the same idea). (It's similar but not equal to the situation of signed
 and unsigned chars in C).
 
 There are several ways to solve this small problem. One of the simpler ways I
 can think of is to deprecate the "byte" type name and introduce a "sbyte" type
 name (that replaces the "byte" type name). Using a sbyte it's probably quite
 more easy to not forget that it's a signed value.
 
 This introduces an inconstancy in the naming scheme of D integral values (they
 are now symmetric, ubyte, byte, int, uint, etc), but it can help avoid some
 bugs, especially from D newbies.


I think byte should be unsigned by default. So I am for sbyte(signed byte - Is
there really anyone who need it?) and byte (unsigned byte)

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Oct 23 2012
prev sibling parent reply d-bugmail puremagic.com writes:
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 I think byte should be unsigned by default. So I am for sbyte(signed byte - Is
 there really anyone who need it?) and byte (unsigned byte)


Ideally I agree with you. In practice D built-in types are prefixed by "u" when

and "sbyte" names pair.

Regarding the usefulness of signed bytes: small data types like ubyte, sbyte,
short, ushort and even float are mostly useful in aggregates, like arrays and
arrays of structs. They are not so useful if you need only one of them.

Recently I have used an array of sbyte values to represent indexes in a short
array (statically known to be shorter than 127 items). Using 1 byte instad of
an int/uint/size_t saves space if you have many of such indexes. And saving
space means reducing cache misses. And to represent those indexes I used a
sbyte instead of a ubyte because I have used -1 to represent "missing value").

sbyte values are not used often, but it's right to have them too in a system
language.

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Oct 23 2012
parent reply "Daniel Kozak" <kozzi11 gmail.com> writes:
On Tuesday, 23 October 2012 at 16:32:38 UTC, 
bearophile_hugs eml.cc wrote:

 And to represent those indexes I used a
 sbyte instead of a ubyte because I have used -1 to represent 
 "missing value").


You still have to use 0xFF :-). But yes, I understand, that sbyte 
and ubyte is better way, how to solve this issue.
Oct 23 2012
parent "Daniel Kozak" <kozzi11 gmail.com> writes:
On Tuesday, 23 October 2012 at 20:04:08 UTC, Daniel Kozak wrote:

 On Tuesday, 23 October 2012 at 16:32:38 UTC, 
 bearophile_hugs eml.cc wrote:

 And to represent those indexes I used a
 sbyte instead of a ubyte because I have used -1 to represent 
 "missing value").


 You still have to use 0xFF :-). But yes, I understand, that 
 sbyte and ubyte is better way, how to solve this issue.


s/have to/can/
Oct 23 2012