re: Write a script to identify an anagram VIEW POST


Scheme R5RS using srfi-13:
First we define a LUT of the first 26 primes.

(define primes '(2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101))

Next we define our function:

(define (isAnagram a b) (let ((mult (lambda (l) (apply * (map (lambda (x) (list-ref primes (- (char->integer x) 97))) (string->list (string-downcase l))))))) (= (mult a) (mult b))))

To break it down, our function takes two string arguments a and b, and applies the internal function 'mult' to both.
Taking a closer look at 'mult':

(mult (lambda (l) (apply * (map (lambda (x) (list-ref primes (- (char->integer x) 97))) (string->list (string-downcase l))))))

It's a lambda expression which takes a string 'l', downcases it, converts it to a list of chars, and maps an anonymous lambda function across that list, then multiplies the resulting list of integers.
Taking a closer look at the anonymous lambda:

lambda (x) (list-ref primes (- (char->integer x) 97))

It quite simply finds the prime number corresponding to the code-point of each character in the list, minus 97 (the code-point for 'a', we can do this because of the earlier downcasing), a number which corresponds to each letter's ordinal value in the alphabet if a corresponds with 0.

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