NAME

CheckDigits::M10_008 - compute check digits for Sedol (GB)

SYNOPSIS

  use Algorithm::CheckDigits;
  $sedol = CheckDigits('sedol');
  if ($sedol->is_valid('0123457')) {
        # do something
  }
  $cn = $sedol->complete('012345');
  # $cn = '0123457'
  $cd = $sedol->checkdigit('0123457');
  # $cd = '7'
  $bn = $sedol->basenumber('0123457');
  # $bn = '012345'

DESCRIPTION

Prior to March 2004 SEDOL codes solely consisted of numbers. Since March 2004 SEDOL codes are a 7 character alphanumeric code.

The structure of the alphanumeric SEDOL codes is one alpha character followed by 5 alphanumeric characters followed by the numerical check digit.

Alpha characters are B-Z excluding vowels.
Alphanumerical characters are 0-9, B-Z excluding vowels.
Numerical Characters are 0-9.

No SEDOL code will be issued without the first alpha character. Active numerical SEDOL codes issued prior to March 2004 remain valid.

ALGORITHM

0: All characters are assigned a numerical value from 0 to 35 where the characters '0' to '9' get 0 to 9, 'B' to 'Z' get 11 to 35 with the position of the vowels kept empty (for instance 'D' gets 13, 'F' gets 15).
1: Beginning left all numbers are weighted with 1,3,1,7,3,9 and 1 (checkdigit)
2: The sum of all products is computed.
3: The check digit is the difference of the sum from step 3 to the next multiple of 10.