[Rd] max on numeric_version with long components

[Kurt Hornik]

>>>>> Kurt Hornik writes:

Should be fixed now.

Best
-k

>>>>> Ivan Krylov via R-devel writes:
> Indeed, apparently using which.min/which.max on the string encoding is
> not good enough.  ? which.min says that x can also be

>   an R object for which the internal coercion to ‘double’ works 

> and I guess we found a case where it does not work.

> I'll look into fixing this, but perhaps we should re-open
> <https://bugs.r-project.org/show_bug.cgi?id=18697> ?

> -k

>> В Sat, 27 Apr 2024 13:56:58 -0500
>> Jonathan Keane <jkeane using gmail.com> пишет:

>>> In devel:
>>> > max(numeric_version(c("1.0.1.100000000", "1.0.3.100000000",  
>>> "1.0.2.100000000")))
>>> [1] ‘1.0.1.100000000’
>>> > max(numeric_version(c("1.0.1.10000000", "1.0.3.10000000",  
>>> "1.0.2.10000000")))
>>> [1] ‘1.0.3.10000000’

>> Thank you Jon for spotting this!

>> This is an unintended consequence of
>> https://bugs.r-project.org/show_bug.cgi?id=18697.

>> The old behaviour of max(<numeric_version>) was to call
>> which.max(xtfrm(x)), which first produced a permutation that sorted the
>> entire .encode_numeric_version(x). The new behavioiur is to call
>> which.max directly on .encode_numeric_version(x), which is faster (only
>> O(length(x)) instead of a sort).

>> What do the encoded version strings look like?

>> x <- numeric_version(c(
>> "1.0.1.100000000", "1.0.3.100000000", "1.0.2.100000000"
>> ))
>> # Ignore the attributes
>> (e <- as.vector(.encode_numeric_version(x)))
>> # [1] "000000001000000000000000001575360400"
>> # [2] "000000001000000000000000003575360400"
>> # [3] "000000001000000000000000002575360400"

>> # order(), xtfrm(), sort() all agree that e[2] is the maximum:
>> order(e)
>> # [1] 1 3 2
>> xtfrm(e)
>> # [1] 1 3 2
>> sort(e)
>> # [1] "000000001000000000000000001575360400"
>> # [2] "000000001000000000000000002575360400"
>> # [3] "000000001000000000000000003575360400"

>> # but not which.max:
>> which.max(e)
>> # [1] 1

>> This happens because which.max() converts its argument to double, which
>> loses precision:

>> (n <- as.numeric(e))
>> # [1] 1e+27 1e+27 1e+27
>> identical(n[1], n[2])
>> # [1] TRUE
>> identical(n[3], n[2])
>> # [1] TRUE

>> Will be curious to know if there is a clever way to keep both the O(N)
>> complexity and the full arbitrary precision.

>> -- 
>> Best regards,
>> Ivan

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