Hmmm, Number::Binary doesn't seem to be taken, at least according to meta::cpan.
What about $enc = Number::Binary->encoder("name"); $dec =
Number::Binary->decoder("name");?
You could also make it easy to get inverse functions by accepting an
object; e.g. $dec = Number::Binary->decoder($enc);
e.g. $e80 = Number::Binary->encoder("intel80")->encode(2.71828)
printf( "%s: %s\n", Number::Binary->name("intel80"),
Number::Binary->decoder("intel80")->decode($e))'
>> Intel extended floating point: 2.71828
Supporting BigXXX for the native value seems important, not only for the
large floats, but some ints.
E.g. Double precision integers (128 bit, or 64 bit on a 32-bit platform
- or 72 bit on a 36-bit platform)
You're the expert; whether the encoders figure out whether bignum was
used in the caller, or the decoder constructors take a "use_big" option,
or the result of decode is specified as a possibly overloaded object
that can do math, or ... I leave to you.
Besides finessing bignums, making the output of decode an object allows
for a path to info methods - besides name, sizes common to all, maybe
things like "smallest number of bits that are needed for this value"
(e.g. would this fit in a smaller format without loss of precision?)
Not sure what the right list would be, but once there's one, it will
probably grow.
Yes, small can get interesting too - e.g. saturating 8-bit bytes packed
in something bigger...
Sounds like fun. Hope this helps. Good luck.
On 03-Jun-21 08:52, Peter John Acklam wrote:
> Thanks for the feedback!
>
> I see your point regarding the Math:: namespace and agree that it
> isn't the best. Alas, Number::Encode is already taken. I suggested
> Number::Pack and Number::Unpack because they aren't taken and because
> of the module's similar functionality to pack() and unpack().
>
> I agree that there should be a simple wrapper and that the format
> should not be a part of the module name specified by the user. I also
> agree about not assuming floating point. Actually, one of the use
> cases is encoding/decoding unsigned 24 bit integers, which are used by
> ImageMagic when reading/writing PAM (portable anymap) images.
>
> There is also Data::IEEE754, but I think the Data:: namespace is too
> general. I will only be dealing with numbers.
>
> Peter
>
> tor. 3. jun. 2021 kl. 13:22 skrev Timothe Litt <tlhack...@cpan.org>:
>> I'd be a bit careful about assuming floating point - will someone want to
>> pack/unpack BCD? Or PDP-10 Gfloat (well, OK that's a floating format)? Or...
>>
>> I don't like Math:: - it implies that it does arithmetic (or calculus, or
>> statistics, or - more than a conversion).
>>
>> And I'd rather not have a format name encoded in the module that the user
>> calls.
>>
>> How about Number::Encode->new("name") & Number::Decode->new("name")?
>>
>> Let "name" get to a subclass, so other formats can be supported just by
>> adding a module - e.g. "Number:Encode::BCD" could be require'd if
>> *->new('bcd') called. Obviously, you'd implement IEEE754, Intel80, and
>> whatever else...
>>
>> Define the API for the subclasses - encode(),decode(), perhaps some info
>> functions (e.g. a printable name, perhaps exponent and fraction range/#bits,
>> ...)
>>
>> Then someone who wants Number::Decode::VAX_DFLOAT just calls
>> Number::Decode->new('vax_dfloat') - after writing it.
>>
>> Some of these can get interesting if you want to decode and actually do math
>> - presumably you'll support Math::BigXxx / bignum? (binary128, VAX
>> H_Floating are, IIRC about 36 decimal digits)
>>
>> And some program that reads archived data can have a description language
>> that is simply "name" "format" "byte offset" "length", and not worry about
>> what module handles what format. In fact, such a program might appreciate
>> the trivial modules Number::Encode::INTEGER32 (and perhaps the less obvious
>> Number::Encode::INTEGER32_ONESCOMPLEMENT)...
>>
>> I suspect there are better names for the format, but the idea is to export a
>> simple wrapper so the next format can be added by anyone, and the callers
>> don't have to know too much.
>>
>> FWIW.
>>
>>
>> On 03-Jun-21 06:23, Peter John Acklam wrote:
>>
>> I also plan to implement the 80 bit "extended precision" format, which
>> is not IEEE 754 compatible. Perhaps the best and simplest is
>> Number::Pack and Number::Unpack?
>>
>> Peter
>>
>> tor. 3. jun. 2021 kl. 11:43 skrev Peter John Acklam <pjack...@gmail.com>:
>>
>> Hi
>>
>> I am working on two modules for encoding and decoding numbers as per
>> IEEE754. The pack() function can encode and decode the formats binary32
>> (single precision) and binary64 (double precision). My module can also
>> handle binary128 (quad precision), binary16 (half precision), bfloat16 (not
>> an IEEE754 format, but it follows the IEEE754 pattern), and a few other
>> formats.
>>
>> My question is about the namespace. Is Math::IEEE754::Encoder (and
>> ...::Decoder) OK? Or is Number::IEEE754::Encoder better? Or any other?
>>
>> Here is an example showing how I use it:
>>
>> my $encoder = Math::IEEE754::Encoder -> new("binary16");
>> my $bytes = $encoder -> (3.14159265358979); # = "\x42\x48"
>>
>> my $decoder = Math::IEEE754::Decoder -> new("binary16");
>> my $number = $decoder -> ($bytes); # = 3.140625
>>
>> The reason for returning an anonymous function rather than implementing the
>> function directly, is speed. There are some constants involved, and I don't
>> want to compute them for each function call.
>>
>> Cheers,
>> Peter John Acklam (PJACKLAM)
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