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Comment by nicoburns | Hacker News Reader

One of the best truly micro features I've seen recently (can't remember which langauge unfortunately - it wasn't a mainstream one), is general binary literal syntax of the form:

    0x[de ad be ef 00]

So much nicer than the usual condensed format. And I think it'd be valid syntax in any language that allows binary integer literal.

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I like that Elixir bitstrings[1] don't have to be bytes. <<2:3>> is three bits 010.

[1] https://elixir-lang.org/getting-started/binaries-strings-and...

A lot of languages allow underscores in numeric literals. Something like 10_000. You can put them anywhere and they get ignored. I don’t know if they also allow it for hex numbers.

> I don’t know if they also allow it for hex numbers.

They do e.g. Python

    >>> 0x_ab_cd_01_23
    2882339107

    >>> 0b_0010_0100
    36

Even C these days, although they chose ' instead of _ :-(

My guess is that they did that because there are real human languages where ' is used as a thousands separator.

There are also real human languages where a space is used as a thousands separator, and an underscore is kind of the programming equivalent of a space.

A half space is British Standard for thousands separator if memory serves, also standard in Norway.

The reason they used quote is outlined in the proposal: https://open-std.org/JTC1/SC22/WG14/www/docs/n2626.pdf

TL;DR is that it's because C++ uses quote. The reason C++ uses quote (they considered underscore) is because of a very obscure feature of C++ called custom literal suffixes which I'd never even heard of, but numbers can be suffixed with a custom identifier, and since single underscore is a valid identifier you can't use that. (https://en.cppreference.com/w/cpp/language/user_literal)

Swiss German for example. But space, half space and dot is also common in Europe. Just not a comma, because this is used as a decimal separator (fractions) in most countries.

It's an interesting mix of "hex" and "array" into one syntactic composition. I do kind-of like it.

Here's how we ended up supporting byte strings (# prefix) in Ecstasy, in this case multi-line:

    Byte[] bytes = #|12 34 56
                    |78 9a BC
                    |dE f0
                   ;

    console.println($|bytes=
                     |{bytes.toHexDump(4)}
                   );

Which prints:

  bytes=
  00: 12 34 56 78 .4Vx
  04: 9A BC DE F0 .¼Þð

Is that giving you a number or a bytestring?

A bytestring I think. Although in statically typed languages there's no reason why it couldn't be both depending on the inferred type.

ohhh that's cool.. in Ruby you can do 0x_dead_beef_00 or any other combo

D's approach would be:

    0xde_ad_be_ef_00

Wouldn't endianness interfere with this notation and the preceding one?

Of course it does - endianness interferes with any sort of numeric literal. Doesn't matter if it's hex, decimal, underscored, whatever.

I think you are missing the point - there is no endianness in normal written text, (or code), but there is endianness when that is translated to an actual number - what order are those bytes intended to be used in?

(Given they have been listed separately rather than as a single number).

What order are the bytes in 0xabcd intended to be used in? I don't see how making it 0x[ab, cd] would be ambiguous, it's the same assumption of reading left to right.

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