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Task/Verhoeff-algorithm/00-TASK.txt

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+;Description
+The [https://en.wikipedia.org/wiki/Verhoeff_algorithm Verhoeff algorithm] is a checksum formula for error detection developed by the Dutch mathematician Jacobus Verhoeff and first published in 1969. It was the first decimal check digit algorithm which detects all single-digit errors, and all transposition errors involving two adjacent digits, which was at the time thought impossible with such a code. 
+
+As the workings of the algorithm are clearly described in the linked Wikipedia article they will not be repeated here. 
+
+;Task:
+Write routines, methods, procedures etc. in your language to generate a Verhoeff checksum digit for non-negative integers of any length and to validate the result. A combined routine is also acceptable.
+
+The more mathematically minded may prefer to generate the 3 tables required from the description provided rather than to hard-code them.
+
+Write your routines in such a way that they can optionally display digit by digit calculations as in the Wikipedia example.
+
+Use your routines to calculate check digits for the integers: '''236''', '''12345''' and '''123456789012''' and then validate them. Also attempt to validate the same integers if the check digits in all cases were '''9''' rather than what they actually are.
+
+Display digit by digit calculations for the first two integers but not for the third. 
+
+;Related task:
+*   [[Damm algorithm]]
+<br><br>
+