• DESCRIPTION</PRE>

DESCRIPTION</PRE> <P> <H2><A NAME=``algorithm''>ALGORITHM</A></H2> <OL> <LI> <CODE>a(1) = 16</CODE> <P><CODE>b(i) = a(i) % 17 +d(i)</CODE>, where <CODE>d(i)</CODE> is the decimal value of the hexdigit at position <EM>i</EM>.</P> <P><CODE>c(i) = b(i) % 16</CODE></P> <P><CODE>a(i) = c(i-1) * 2</CODE>, for <EM>i</EM> greater than 1</P> <P></P> <LI> Beginning left for each <EM>i</EM> = 1..16, <CODE>a</CODE>, <CODE>b</CODE>, <CODE>c</CODE> are computed. <P></P> <LI> The check digit is the value for <CODE>d(16)</CODE> where <CODE>c(16)</CODE> equals 1. <P></P> <LI> The check digit is appended as hexadecimal value to the number. <P></P></OL> <P> <H2><A NAME=``methods''>METHOD/A</H2> <DL> <DT><STRONG><A NAME=``item_is_valid''><CODE>is_valid($number)</CODE></A></STRONG><BR> <DD> Returns true only if <CODE>$number</CODE> consists solely of numbers and the last digit is a valid check digit according to the algorithm given above. <P>Returns false otherwise,</P> <P></P> <DT><STRONG><A NAME=``item_complete''><CODE>complete($number)</CODE></A></STRONG><BR> <DD> The check digit for <CODE>$number</CODE> is computed and concatenated to the end of <CODE>$number</CODE>. <P>Returns the complete number with check digit or '' if <CODE>$number</CODE> does not consist solely of digits and spaces.</P> <P></P> <DT><STRONG><A NAME=``item_basenumber''><CODE>basenumber($number)</CODE></A></STRONG><BR> <DD> Returns the basenumber of <CODE>$number</CODE> if <CODE>$number</CODE> has a valid check digit. <P>Return '' otherwise.</P> <P></P> <DT><STRONG><A NAME=``item_checkdigit''><CODE>checkdigit($number)</CODE></A></STRONG><BR> <DD> Returns the checkdigit of <CODE>$number</CODE> if <CODE>$number</CODE> has a valid check digit. <P>Return '' otherwise.</P> <P></P></DL> <P> <H2><A NAME=``export''>EXPORT</A></H2> <P>None by default.</P> <P> <HR> <H1><A NAME=``author''>AUTHOR</A></H1> <P>Mathias Weidner, &lt;<A HREF=``mailto:mathias@weidner.in-bad-schmiedeberg.de''>mathias@weidner.in-bad-schmiedeberg.de&gt;</P> <P> <HR> <H1><A NAME=``see also''>SEE ALSO</A></H1> <P><A HREF=``../../../../bin/perl.html''>the perl manpage</A>, <A HREF=``../../../../site/lib/CheckDigits.html''>the CheckDigits manpage</A>, <EM>www.pruefziffernberechnung.de</EM>.</P> <TABLE BORDER=0 CELLPADDING=0 CELLSPACING=0 WIDTH=100%> <TR><TD CLASS=block VALIGN=MIDDLE WIDTH=100% BGCOLOR=``#cccccc''> <FONT SIZE=+1><STRONG><P CLASS=block>&nbsp;CheckDigits::M16_001 - compute check digits for ISAN</P></STRONG></FONT> </TD></TR> </TABLE>

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