OCaml needs an arbitrary-precision decimal type

[yawaramin]

I’ve mentioned this before: What libraries are missing?

But pulling it into a new thread because I have a specific ask: is someone willing to contribute a decimal number implementation to OCaml?

I realize OCaml has historically had a minimalist standard library philosophy, e.g. it’s reasonable to not include a JSON data type, but I believe decimal numbers are a fairly fundamental type especially for business applications. Major industrial language platforms tend to agree:

• .NET: https://docs.microsoft.com/en-us/dotnet/api/system.decimal?view=netcore-3.1
• Java: https://docs.oracle.com/javase/8/docs/api/java/math/BigDecimal.html
• Python: https://docs.python.org/3.8/library/decimal.html
• Ruby: https://ruby-doc.org/stdlib-2.5.1/libdoc/bigdecimal/rdoc/BigDecimal.html
• ObjC/Swift: https://developer.apple.com/documentation/foundation/decimal

And even newer ones:

• Crystal: https://crystal-lang.org/api/0.24.2/BigDecimal.html
• Zig (proposed): https://github.com/ziglang/zig/issues/4221

So, I thought I’d bring it up again, as it’s really pretty foundational IMHO.

[Drup]

You’re going at this wrong.

The first step of putting anything in the stdlib is to actually write a library that does it.

So, if you want it, start by writing the library. Publish it, iterate on the design and then maybe propose it. Worse case, you’ll have a good decimal library.

[yawaramin]

Well, I really do believe it should be in the standard library, but I have nothing against starting it as a separate package. In either case, my main question is still: is anyone willing to contribute one?

[Yaron_Minsky]

I’ve kicked off the process of releasing Jane Street’s arbitrary precision decimal type, called Bigdecimal. It should hit github in a few days, I expect.

y

[yawaramin]

Thank you very much, that is very generous. I’ve been working on a straight-up port of the Python decimal module to OCaml for the past few days, but of course Jane Street’s Bigdecimal will be much more trustworthy than my home-grown effort

[Yaron_Minsky]

Our Bigdecimal library is now live:

janestreet/bigdecimal

It won’t be in the ordinary Opam repo until our next stable release, which is scheduled for early 2021.