Floating point issue

The following function, 'bitC' from ?numToBits, displays the bits in a
double precision number, separated into the sign bit, the 11 exponent bits,
and the 52 bits in the mantissa.  I've shown the results with your numbers
from R-2.4.0 on my Windows 11 Lenovo laptop: what do you get?

bitC <- function(x) noquote(vapply(as.double(x), function(x) { # split

one double
+     b <- substr(as.character(rev(numToBits(x))), 2L, 2L)
+     paste0(c(b[1L], " ", b[2:12], " | ", b[13:64]), collapse = "")
+   }, ""))

bitC(10^25)

# [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001

bitC(10000000000000000905969664)

# [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001

bitC(10000000000000000905969664 - 10^25)

# [1] 0 00000000000 | 0000000000000000000000000000000000000000000000000000

bitC(1e25)

# [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001

-Bill

On Sun, Jul 10, 2022 at 7:00 AM Antoine Fabri <antoine.fabri at gmail.com>
wrote:

Dear r-devel,

For some numbers, the printed value is not equivalent to the input :

options(scipen = 999)
## GOOD
1e24
#> [1]  999999999999999983222784
1e24 == 999999999999999983222784
#> [1] TRUE

## BAD
1e25
#> [1] 10000000000000000905969664
1e25 == 10000000000000000905969664
#> [1] FALSE

## STILL BAD
10000000000000000905969664
#> [1] 10000000000000003053453312

## GOOD AGAIN
10000000000000003053453312
#> [1] 10000000000000003053453312

# Additionally
10000000000000000000000000 == 1e25
#> [1] FALSE

Are these bugs ?

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