CODEWITHSUNDEEP
schemeracket
Juan C. Moreno
Juan C. Moreno

Reputation: 35

How to convert string into a list of integers in scheme?

How can I convert a string of digits to a list of integers ? I want "1234" to be converted to list 1 2 3 4

Upvotes: 2

Views: 1307

Answers (1)

Sylwester
Sylwester

Reputation: 48745

You can convert a string to a list of chars with string->list. Eg.

(string->list "1234") ; ==> (#\1 #\2 #\3 #\4)

You can convert a char to it's ascii value with char->integer. Eg. 

(char->integer #\1) ; ==> 49

The Ascii values for #\0 ... #\9 are in ascending order so you can substract to get the digit value:

(- (char->integer #\1) 48) ; ==> 1

Create a procedure where you combine these with map and you are good to go.

(define (number-string->number-list str)
  (map (lambda (ch) 
         <??>)
       (string->list str)))

(number-string->number-list "1234") ; ==> (1 2 3 4)

Upvotes: 5

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