Re: Module namespace for IEEE754 encoder/decoder

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 <[email protected]>:
>
> 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)