NAME

       valtype::creditcard::amex - Validation for AMEX creditcard number

SYNOPSIS

       package require Tcl  8.5

       package require snit  2

       package require valtype::common

       package require valtype::luhn

       package require valtype::creditcard::amex  ?1?

       valtype::creditcard::amex validate value

       valtype::creditcard::amex checkdigit value

________________________________________________________________________________________________________________

DESCRIPTION

       This package implements a snit validation type for an AMEX creditcard number.

       A  validation  type  is  an  object  that  can  be used to validate Tcl values of a particular kind.  For
       example, snit::integer, a validation type defined by the snit package is used  to  validate  that  a  Tcl
       value is an integer.

       Every  validation  type has a validate method which is used to do the validation. This method must take a
       single argument, the value to be validated; further, it must do nothing if the value is valid, but  throw
       an error if the value is invalid:

                  valtype::creditcard::amex validate .... ;# Does nothing
                  valtype::creditcard::amex validate .... ;# Throws an error (bad American Expresss creditcard number).

       The  validate  method will always return the validated value on success, and throw the -errorcode INVALID
       on error, possibly with additional elements which provide more details about the problem.

API

       The API provided by this package satisfies the specification  of  snit  validation  types  found  in  the
       documentation of Snit's Not Incr Tcl.

       valtype::creditcard::amex validate value
              This method validates the value and returns it, possibly in a canonical form, if it passes. If the
              value does not pass the validation an error is thrown.

       valtype::creditcard::amex checkdigit value
              This method computes a check digit for the value. Before doing so it is validated,  except  for  a
              checkdigit. If the value does not pass the validation no check digit is calculated and an error is
              thrown instead.

ERROR CODES

       As said in the package description, the errors thrown by the commands of  this  package  in  response  to
       input  validation  failures  use  the  -errorcode INVALID to distinguish themselves from package internal
       errors.

       To provide more detailed information about why the validation failed the -errorCode goes actually  beyond
       that.   First,  it  will  contain a code detailing the type itself. Here this is CREDITCARD AMEX. This is
       then followed by values detailing the reason for the failure. The full set of -errorCodes  which  can  be
       thrown by this package are:

       INVALID CREDITCARD AMEX CHARACTER
              The  input value contained one or more bad characters, i.e. characters which must not occur in the
              input for it to be an AMEX creditcard number.

       INVALID CREDITCARD AMEX CHECK-DIGIT
              The check digit of the input value is wrong. This usually signals a data-entry error, with  digits
              transposed, forgotten, etc. Of course, th input may be an outright fake too.

       INVALID CREDITCARD AMEX LENGTH
              The input value is of the wrong length to be an AMEX creditcard number.

       INVALID CREDITCARD AMEX PREFIX
              The  input  value  does not start with the magic value(s) required for it to be an AMEX creditcard
              number.

BUGS, IDEAS, FEEDBACK

       This document, and the package it describes, will undoubtedly contain bugs and  other  problems.   Please
       report  such  in  the  category  valtype  of  the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist].
       Please also report any ideas for enhancements you may have for either package and/or documentation.

       When proposing code changes, please provide unified diffs, i.e the output of diff -u.

       Note further that attachments are strongly preferred over inlined patches. Attachments  can  be  made  by
       going  to the Edit form of the ticket immediately after its creation, and then using the left-most button
       in the secondary navigation bar.

KEYWORDS

       AMEX, American Express, Checking, Testing, Type checking, Validation,  Value  checking,  bank,  card  for
       credit, credit card, finance, isA

CATEGORY

       Validation, Type checking

COPYRIGHT

       Copyright (c) 2011 Andreas Kupries <andreas_kupries@users.sourceforge.net>