Re: Module namespace for IEEE754 encoder/decoder

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 <[email protected]>:
>> 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)