valtype::verhoeff(3tcl)

NAME
valtype::verhoeff - Validation for plain number with a VERHOEFF checkdigit

SYNOPSIS
package require Tcl 8.5 9

package require snit 2

package require valtype::common

package require valtype::verhoeff ?1.1?

valtype::verhoeff validate value

valtype::verhoeff checkdigit value

DESCRIPTION
This package implements a snit validation type for a plain number with a VERHOEFF checkdigit.

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::verhoeff validate .... ;# Does nothing
        valtype::verhoeff validate .... ;# Throws an error (bad verhoeff checkdigit).

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::verhoeff 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::verhoeff 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 VERHOEFF. 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 VERHOEFF CHARACTER
    The input value contained one or more bad characters, i.e. characters which must not occur in the input for it to be a plain number with a VERHOEFF checkdigit.

INVALID VERHOEFF 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.

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
Checking, Testing, Type checking, Validation, Value checking, isA, verhoeff

CATEGORY
Validation, Type checking

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