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Re: Rosetta PGA-TRAM

by Arunbear (Prior)
on Feb 11, 2011 at 17:46 UTC ( #887659=note: print w/replies, xml ) Need Help??

in reply to Rosetta PGA-TRAM

This is an implementation with lots of parentheses :)
#lang scheme (define (sum-of-ints li [sum 0]) (if [< (length li) 2] (+ sum (apply + li)) (let ([f (first li)] [s (second li)]) (if [> s f] (sum-of-ints (cddr li) (+ sum (- s f))) (sum-of-ints (cdr li) (+ sum f)))))) (define roman-to-dec '()) (set! roman-to-dec (let ([rtoa #hash((#\M . 1000) (#\D . 500) (#\C . 100) (#\L . 50) (#\X . 10) (#\V . 5) (#\I . 1))]) (lambda (roman) (sum-of-ints (map (lambda (x) (hash-ref rtoa x)) (string->list (string-upcase roman))))))) (define test-data '("XLII" "LXIX" "mi" "MCMLXXXV")) (for ([r test-data]) (printf "~a ~a~n" r (roman-to-dec r)))
+% mzscheme XLII 42 LXIX 69 mi 1001 MCMLXXXV 1985
Like the perl version, it uses a lexical scope to hide the hash.

It however uses a method of combining the numbers that is closer to how we'd do it in our heads i.e. following the Subtractive principle

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