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33 lines
1.5 KiB
Plaintext
33 lines
1.5 KiB
Plaintext
These subroutines tell you whether a credit card number is
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self-consistent -- whether the last digit of the number is
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a valid checksum for the preceding digits.
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The validate() subroutine returns 1 if the card number
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provided passes the checksum test, and 0 otherwise.
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The cardtype() subroutine returns a string containing the
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type of card: "MasterCard", "VISA", and so on. My list is
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not complete; I welcome additions.
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The generate_last_digit() subroutine computes and returns
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the last digit of the card given the preceding digits.
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With a 16-digit card, you provide the first 15 digits; the
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subroutine returns the sixteenth.
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This module does not tell you whether the number is on an
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actual card, only whether it might conceivably be on a
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real card. To verify whether a card is real, or whether
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it's been stolen, or what its balance is, you need a
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Merchant ID, which gives you access to credit card
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databases. The Perl Journal
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(http://work.media.mit.edu/tpj) has a Merchant ID so that
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I can accept MasterCard and VISA payments; it comes with
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the little pushbutton/slide-your-card-through device
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you've seen in restaurants and stores. That device
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calculates the checksum for you, so I don't actually use
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this module.
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These subroutines will also work if you provide the
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arguments as numbers instead of strings, e.g.
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validate(5276440065421319).
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