'\"
'\" Generated from file 'vtype\&.inc' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2011 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
'\"
.TH "valtype::luhn" n 1\&.1 tcllib "Validation types"
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.SH NAME
valtype::luhn \- Validation for plain number with a LUHN checkdigit
.SH SYNOPSIS
package require \fBTcl 8\&.5 9\fR
.sp
package require \fBsnit 2\fR
.sp
package require \fBvaltype::common\fR
.sp
package require \fBvaltype::luhn ?1\&.1?\fR
.sp
\fBvaltype::luhn\fR \fBvalidate\fR \fIvalue\fR
.sp
\fBvaltype::luhn\fR \fBcheckdigit\fR \fIvalue\fR
.sp
.BE
.SH DESCRIPTION
This package implements a snit validation type for a plain number with a LUHN checkdigit\&.
.PP
A validation type is an object that can be used to validate Tcl values
of a particular kind\&.  For example, \fBsnit::integer\fR, a validation
type defined by the \fBsnit\fR package is used to validate that a
Tcl value is an integer\&.
.PP
Every validation type has a \fBvalidate\fR 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:
.CS


    valtype::luhn validate \&.\&.\&.\&. ;# Does nothing
    valtype::luhn validate \&.\&.\&.\&. ;# Throws an error (bad luhn checkdigit)\&.

.CE
.PP
The \fBvalidate\fR method will always return the validated value on
success, and throw the \fB-errorcode\fR INVALID on error, possibly
with additional elements which provide more details about the problem\&.
.SH API
The API provided by this package satisfies the specification
of snit validation types found in the documentation of
\fISnit's Not Incr Tcl\fR\&.
.TP
\fBvaltype::luhn\fR \fBvalidate\fR \fIvalue\fR
This method validates the \fIvalue\fR and returns it, possibly in a
canonical form, if it passes\&. If the value does not pass the
validation an error is thrown\&.
.TP
\fBvaltype::luhn\fR \fBcheckdigit\fR \fIvalue\fR
This method computes a check digit for the \fIvalue\fR\&. 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\&.
.PP
.SH "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
\fB-errorcode\fR INVALID to distinguish themselves from package
internal errors\&.
.PP
To provide more detailed information about why the validation
failed the \fB-errorCode\fR goes actually beyond that\&.
First, it will contain a code detailing the type itself\&. Here this is
\fBLUHN\fR\&. This is then followed by values detailing the
reason for the failure\&. The full set of \fB-errorCode\fRs which can
be thrown by this package are:
.TP
INVALID LUHN 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 LUHN checkdigit\&.
.TP
INVALID LUHN 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\&.
.PP
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fIvaltype\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH KEYWORDS
Checking, Testing, Type checking, Validation, Value checking, isA, luhn
.SH CATEGORY
Validation, Type checking
.SH COPYRIGHT
.nf
Copyright (c) 2011 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>

.fi
