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.

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>