Validate International Securities Identification Number: Difference between revisions

=={{header|FreeBASIC}}==

<lang freebasic>' version 27-10-2016

' compile with: fbc -s console

#Ifndef TRUE ' define true and false for older freebasic versions

#Define FALSE 0

#Define TRUE Not FALSE

#EndIf

Function luhntest(cardnr As String) As Long

cardnr = Trim(cardnr) ' remove spaces

Dim As String reverse_nr = cardnr

Dim As Long i, j, s1, s2, l = Len(cardnr) -1

' reverse string

For i = 0 To l

reverse_nr[i] = cardnr[l - i]

Next

' sum odd numbers

For i = 0 To l Step 2

s1 = s1 + (reverse_nr[i] - Asc("0"))

Next

' sum even numbers

For i = 1 To l Step 2

j = reverse_nr[i] - Asc("0")

j = j * 2

If j > 9 Then j = j Mod 10 +1

s2 = s2 + j

Next

If (s1 + s2) Mod 10 = 0 Then

Return TRUE

Else

Return FALSE

End If

End Function

' ------=< MAIN >=-----

Dim As String test_str

Dim As String test_set(1 To ...) = { "US0378331005", "US0373831005", _

"U50378331005", "US03378331005", "AU0000XVGZA3", _

"AU0000VXGZA3", "FR0000988040" }

Dim As Long i, l, n, x

For i = 1 To UBound(test_set)

test_str = ""

l = Len(test_set(i))

If l <> 12 Then

Print test_set(i), "Invalid, length <> 12 char."

Continue For

End If

If test_set(i)[0] < Asc("A") Or test_set(i)[1] < Asc("A") Then

Print test_set(i), "Invalid, number needs to start with 2 characters"

Continue For

End If

For n = 0 To l -1

x = test_set(i)[n] - Asc("0")

' if test_set(i)[i] is a letter we to correct for that

If x > 9 Then x = x -7

If x < 10 Then

test_str = test_str + Str(x)

Else ' two digest number

test_str = test_str + Str(x \ 10) + Str(x Mod 10)

End If

Next

Print test_set(i), IIf(luhntest(test_str) = TRUE, "Valid","Invalid, checksum error")

Next

' empty keyboard buffer

While InKey <> "" : Wend

Print : Print "hit any key to end program"

Sleep

End</lang>

{{out}}

<pre>US0378331005 Valid

US0373831005 Invalid, checksum error

U50378331005 Invalid, number needs to start with 2 characters

US03378331005 Invalid, length <> 12 char.

AU0000XVGZA3 Valid

AU0000VXGZA3 Valid

FR0000988040 Valid</pre>