Underscores only every 2^n digits in non-decimal numbers

[l0b0]

What it does: Warns if an integral or floating point non-decimal number is split somewhere other than between n^2 and (n^2)+1 (for constant n≥1). Hexadecimal, octal and binary numbers are used when dealing with 2^n fractions or multiples of bytes.

Examples:

• 0xabc_def. Probably what was meant was 0xab_cdef, 0xab_cd_ef or there's a missing nibble in the second half.
• 0xa_b_c_d_e_f is more verbose but no clearer than 0xabcdef.

[Manishearth]

I see use cases for splitting this at other points (e.g. a bit mask with different groups of masks) but that seems minor in this case and there aren't other issues so this seems fine.

Though the description isn't quite accurate, it should be between powers of four.

[l0b0]

Though the description isn't quite accurate, it should be between powers of four.

In most cases I'd agree, but I guess a fairly common pattern would be splitting hexadecimal between bytes, as in 0xab_cd_ef.

[Manishearth]

Sorry, powers of eight. Not n^2

[l0b0]

Ah, we meant the same thing. To clarify, I meant the most natural splits are nibbles (0b1111_0000) or bytes (0b11111111_00000000) for binary, and bytes (0xff) or words for hex.