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Digital root: Difference between revisions
Added a Scheme implementation.
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(Added a Scheme implementation.) |
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393900588225 has additive persistance 2 and digital root of 9
7e0 has additive persistance 2 and digital root of 6</pre>
=={{header|Scheme}}==
{{works with|Chez Scheme}}
<lang scheme>; Convert an integer into a list of its digits.
(define integer->list
(lambda (integer)
(let loop ((list '()) (int integer))
(if (< int 10)
(cons int list)
(loop (cons (remainder int 10) list) (quotient int 10))))))
; Return the sum of the digits of an integer.
(define integer-sum-digits
(lambda (integer)
(fold-left + 0 (integer->list integer))))
; Compute the digital root (additive) and additive persistence of an integer.
; Return as a cons of (adr . ap).
(define adr-ap
(lambda (integer)
(let loop ((int integer) (cnt 0))
(if (< int 10)
(cons int cnt)
(loop (integer-sum-digits int) (1+ cnt))))))
; Emit a table of integer, digital root (additive), and additive persistence
; for the example integers given.
(printf "~13@a ~6@a ~6@a~%" "Integer" "Root" "Pers.")
(let rowloop ((intlist '(627615 39390 588225 393900588225 0 1 68010887038)))
(when (pair? intlist)
(let* ((int (car intlist))
(aa (adr-ap int)))
(printf "~13@a ~6@a ~6@a~%" int (car aa) (cdr aa))
(rowloop (cdr intlist)))))</lang>
{{out}}
<pre> Integer Root Pers.
627615 9 2
39390 6 2
588225 3 2
393900588225 9 2
0 0 0
1 1 0
68010887038 4 3</pre>
=={{header|Seed7}}==
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