Re^5: Why am I losing accuracy?

[syphilis]

Not exactly (a small loss of precision at the very end of each number).

I think bliako's script works flawlessly if "accuracy" and "precision" are not specified:

use strict;
use warnings;

use Math::BigInt;
use Digest::SHA qw(sha256_hex);

for(my $i=1;$i<=10;$i++){
    # the sha as a hex string (no '0x' prepended)
    my $hexstr = sha256_hex($i);

    # to create a bigint from a hex string we need to prepend '0x' to 
+it
    my $digest = Math::BigInt->new('0x'.$hexstr);

    # operate
    print "$i $digest\n";
    $digest /= 64;
    print "$i $digest\n";
}

Outputs:

1 48635463943209834798109814161294753926839975257569795305637098542720
[phone]
1 75992912411265366872046584627023053010687461339952805165057966473001
+0295661
2 96094161643976066833367867971426158458230048495430276217795328666133
[phone]
2 15014712756871260442713729370535337259098445077410980659030520104083
[phone]
3 35293215426786447154857697798367884701614677727176325092965345248689
[phone]
3 55145649104353823679465152809949819846272933948713007957758351951076
+8833151
4 33984360982413536682390860969296307922929415152052354251133793603654
[phone]
4 53100564035021151066235720264525481129577211175081803517396552505710
+1064958
5 10818240655469999731486825095773005325907358940236581977057259273658
[phone]
5 16903501024171874580448164212145320821730248344119659339151967615091
[phone]
6 10492023800686533720501340709024820017001830686534338836405100876796
[phone]
6 16393787188572708938283344857851281276565360447709904431882970119994
[phone]
7 54734117258892461880478870895348100103198302433611928089023761078319
[phone]
7 85522058217019471688248235773981406411247347552518637639099626684874
+2304913
8 20075373234943686845167158285967784892467090849631486320124245130906
[phone]
8 31367770679599510695573684821824663894479829452549197375194133017041
+5934866
9 11463511883541201508393500803711559652562721115888819482889049505863
[phone]
9 17911737318033127356864845005799311957129251743576280442014139852911
+1617238
10 3359281535163583886622750554468341756416232122807515421831543601247
[phone]

Cheers,
Rob

[vr]

Perhaps, misunderstanding began with

I think you need to set the precision to 1

which maybe stemmed from

p or precision ... 0 or 1 mean round to integer

which (i.e., Perl core module documentation) is wrong. "0" is "round to integer". "1" is not.

Allowing "accuracy" and "precision" for extended integers (through a pragma i.e. infecting everything which interacts with source code literals!) is, simply, very evil and can lead to bizarre infinite loops, as shown, but it's not a bug in itself, because documented (but should never be used (?))