Re: Turning very larger numbers into an array of bits

A better way using vec in 8-bit chunks to store the modulo of the number and 256. This places the least significant bit first as you required.

use strict;
use warnings;

use feature qw{ say };

my $val = 107865;

# Pre-size the vector for 80 bits.
#
my $vec;
vec( $vec, 79, 1 ) = 0;

my $offset = 0;

while ( $val >= 256 )
{
    my $rem = $val % 256;
    vec( $vec, $offset ++, 8 ) = $rem;
    $val /= 256;
}
vec( $vec, $offset, 8 ) = $val;

say unpack q{b*}, $vec;

say qq{Bit $_: }, vec( $vec, $_, 1 ) ? q{set} : q{not set}
   for 0 .. 79;
[download]

The output.

1001101010100101100000000000000000000000000000000000000000000000000000
+0000000000
Bit 0: set
Bit 1: not set
Bit 2: not set
Bit 3: set
Bit 4: set
Bit 5: not set
Bit 6: set
Bit 7: not set
Bit 8: set
Bit 9: not set
Bit 10: set
Bit 11: not set
Bit 12: not set
Bit 13: set
Bit 14: not set
Bit 15: set
Bit 16: set
Bit 17: not set
Bit 18: not set
Bit 19: not set
Bit 20: not set
Bit 21: not set
Bit 22: not set
Bit 23: not set
Bit 24: not set
Bit 25: not set
Bit 26: not set
Bit 27: not set
Bit 28: not set
Bit 29: not set
Bit 30: not set
Bit 31: not set
Bit 32: not set
Bit 33: not set
Bit 34: not set
Bit 35: not set
Bit 36: not set
Bit 37: not set
Bit 38: not set
Bit 39: not set
Bit 40: not set
Bit 41: not set
Bit 42: not set
Bit 43: not set
Bit 44: not set
Bit 45: not set
Bit 46: not set
Bit 47: not set
Bit 48: not set
Bit 49: not set
Bit 50: not set
Bit 51: not set
Bit 52: not set
Bit 53: not set
Bit 54: not set
Bit 55: not set
Bit 56: not set
Bit 57: not set
Bit 58: not set
Bit 59: not set
Bit 60: not set
Bit 61: not set
Bit 62: not set
Bit 63: not set
Bit 64: not set
Bit 65: not set
Bit 66: not set
Bit 67: not set
Bit 68: not set
Bit 69: not set
Bit 70: not set
Bit 71: not set
Bit 72: not set
Bit 73: not set
Bit 74: not set
Bit 75: not set
Bit 76: not set
Bit 77: not set
Bit 78: not set
Bit 79: not set
[download]

I hope this solution better fits your requirements.

Update: The condition in the while was incorrect, changed from $val > 256 to $val >= 256 to rectify invalid results for values exactly divisible by 256 to the n.

Cheers,

JohnGG

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