27 lines
1002 B
Racket
27 lines
1002 B
Racket
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#lang racket
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(define (sum lst) ;define sum function
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(define (helper lst sum) ;setup tail recursive helper
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(cond ;conditions for recursion
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[(empty? lst) 0] ;base case
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[else (if ;case for if the list item is a number
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(number? (first lst)) ;if the item is a number
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(helper ((rest lst) (+ sum (first lst)))) ;call the helper function with the rest of the list and add to sum
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(helper (rest lst) sum)) ;error case if it is not a number
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]))
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(helper lst 0)) ;first recursive call
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;my attempet to use match, was not going well
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;(match lst
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; [`() 0]
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; [(number? head tail ...) (+ sum head)
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(module+ test
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(require rackunit)
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(check-equal? (sum `()) 0)
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(check-equal? (sum `(1 2)) 3)
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(check-equal? (sum `(1 2 "buckle my shoe")) 3)
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(check-equal? (sum `(-1 -2)) -3) ;test for negative numbers
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(check-equal? (sum `(-1 `(1 2) -2))) ;test for recursive lists
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(check-equal? (sum `(0.1 0.2)) 0.3) ;test for floating point numbers
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)
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