Task: Validate International Securities Identification Number







Python: def check_isin(a):
    if len(a) != 12 or not all(c.isalpha() for c in a[:2]) or not all(c.isalnum() for c in a[2:]):
        return False
    s = "".join(str(int(c, 36)) for c in a)
    return 0 == (sum(sum(divmod(2 * (ord(c) - 48), 10)) for c in s[-2::-2]) +
                 sum(ord(c) - 48 for c in s[::-2])) % 10


def check_isin_alt(a):
    if len(a) != 12:
        return False
    s = []
    for i, c in enumerate(a):
        if c.isdigit():
            if i < 2:
                return False
            s.append(ord(c) - 48)
        elif c.isupper():
            if i == 11:
                return False
            s += divmod(ord(c) - 55, 10)
        else:
            return False
    v = sum(s[::-2])
    for k in s[-2::-2]:
        k = 2 * k
        v += k - 9 if k > 9 else k
    return v % 10 == 0

[check_isin(s) for s in ["US0378331005", "US0373831005", "U50378331005", "US03378331005",
                         "AU0000XVGZA3", "AU0000VXGZA3", "FR0000988040"]]





COBOL:         >>SOURCE FORMAT FREE

identification division.
program-id. callISINtest.
data division.
working-storage section.
01  ISINtest-result binary-int.
procedure division.
start-callISINtest.
    display 'should be valid ' with no advancing
    call 'ISINtest' using 'US0378331005' ISINtest-result
    perform display-ISINtest-result
    display 'should not be valid ' with no advancing
    call 'ISINtest' using 'US0373831005' ISINtest-result
    perform display-ISINtest-result
    display 'should not be valid ' with no advancing
    call 'ISINtest' using 'U50378331005' ISINtest-result
    perform display-ISINtest-result
    display 'should not be valid ' with no advancing
    call 'ISINtest' using 'US03378331005' ISINtest-result
    perform display-ISINtest-result
    display 'should be valid ' with no advancing
    call 'ISINtest' using 'AU0000XVGZA3' ISINtest-result
    perform display-ISINtest-result
    display 'should be valid ' with no advancing
    call 'ISINtest' using 'AU0000VXGZA3' ISINtest-result
    perform display-ISINtest-result
    display 'should be valid ' with no advancing
    call 'ISINtest' using 'FR0000988040' ISINtest-result
    perform display-ISINtest-result
    stop run
    .
display-ISINtest-result.
    evaluate ISINtest-result
    when 0 
        display ' is valid'
    when -1
        display ' invalid length '
    when -2
        display ' invalid countrycode '
    when -3
        display ' invalid base36 digit '
    when -4
        display ' luhn test failed'
    when other
        display ' invalid return code ' ISINtest-result
    end-evaluate
    .
end program callISINtest.

identification division.
program-id. ISINtest.
data division.
working-storage section.
01  country-code-values value
    'ADAEAFAGAIALAMAOAQARASATAUAWAXAZBABBBDBEBFBGBHBIBJBLBMBNBOBQBRBS'
&   'BTBVBWBYBZCACCCDCFCGCHCICKCLCMCNCOCRCUCVCWCXCYCZDEDJDKDMDODZECEE'
&   'EGEHERESETFIFJFKFMFOFRGAGBGDGEGFGGGHGIGLGMGNGPGQGRGSGTGUGWGYHKHM'
&   'HNHRHTHUIDIEILIMINIOIQIRISITJEJMJOJPKEKGKHKIKMKNKPKRKWKYKZLALBLC'
&   'LILKLRLSLTLULVLYMAMCMDMEMFMGMHMKMLMMMNMOMPMQMRMSMTMUMVMWMXMYMZNA'
&   'NCNENFNGNINLNONPNRNUNZOMPAPEPFPGPHPKPLPMPNPRPSPTPWPYQARERORSRURW'
&   'SASBSCSDSESGSHSISJSKSLSMSNSOSRSSSTSVSXSYSZTCTDTFTGTHTJTKTLTMTNTO'
&   'TRTTTVTWTZUAUGUMUSUYUZVAVCVEVGVIVNVUWFWSYEYTZAZMZW'.
    03  country-codes occurs 249
        ascending key country-code
        indexed by cc-idx.
        05  country-code pic xx.

01  b pic 99.
01  base36-digits pic x(36) value
    '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'.

01  i pic 99.
01  p pic 99.
01  luhn-number pic x(20).
01  luhntest-result binary-int.

linkage section.
01  test-number any length.
01  ISINtest-result binary-int.

procedure division using test-number ISINtest-result.
start-ISINtest.
    display space test-number with no advancing

    
    if function length(test-number) <> 12
        move -1 to ISINtest-result
        goback
    end-if

    
    search all country-codes
    at end
        move -2 to ISINtest-result
        goback
    when test-number(1:2) = country-code(cc-idx)
        continue 
    end-search

    
    
    move 0 to p
    perform varying i from 1 by 1 until i > 12
        if test-number(i:1) >= '0' and <= '9'
            move test-number(i:1) to luhn-number(p + 1:1)
            add 1 to p
        else
            perform varying b from 9 by 1 until b > 35
            or base36-digits(b + 1:1) = test-number(i:1)
                continue
            end-perform
            if b > 35
                 move -3 to ISINtest-result
                 goback
            end-if
            move b to luhn-number(p + 1:2)
            add 2 to p
        end-if
    end-perform

    call 'luhntest' using luhn-number(1:p) luhntest-result
    if luhntest-result <> 0
        move -4 to ISINtest-result
        goback
    end-if

    move 0 to ISINtest-result
    goback
    .
end program ISINtest.

identification division.
program-id. luhntest.
data division.
working-storage section.
01  i pic S99.
01  check-sum pic 999.
linkage section.
01  test-number any length.
01  luhntest-result binary-int.
procedure division using test-number luhntest-result.
start-luhntest.
    display space test-number with no advancing
    move 0 to check-sum

    
    compute i = function length(test-number)
    perform varying i from i by -2 until i < 1
        add function numval(test-number(i:1)) to check-sum
    end-perform
    display space check-sum with no advancing

    
    compute i = function length(test-number) - 1
    perform varying i from i by -2 until i < 1
        add function numval(test-number(i:1)) to check-sum
        add function numval(test-number(i:1)) to check-sum
        
        if test-number(i:1) >= '5'
            subtract 9 from check-sum
        end-if
    end-perform
    display space check-sum with no advancing

    if function mod(check-sum,10) = 0
        move 0 to luhntest-result 
    else
        move -1 to luhntest-result 
    end-if
    goback
    .
end program luhntest.