Converting String to integer in Scheme

Question

How can I convert a string of digits to an integer ? I want "365" to be converted to 365.

What I have tried, string->list then char->integer, but this returns ASCII value of that integer, how can I get that integer ?

Please help.

Possible duplicate [here](http://stackoverflow.com/questions/8956789/read-number-in-or-something-can-turn-string-e-g-1-to-integer-1-in-racket/8956947#8956947) — Inaimathi, Oct 15 '13 at 14:48

score 36 · Accepted Answer · answered Oct 15 '13 at 10:56

36

Try: string->number

> (string->number "1234")
1234

answered Oct 15 '13 at 10:56

DJG

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ahha, i didn't try this. I was going by some long way, anyways Thanks – Hari Chaudhary Oct 15 '13 at 11:15
Related: http://stackoverflow.com/questions/23027030/how-can-i-convert-a-string-into-exact-number-in-scheme-lisp – Felipe Apr 12 '14 at 07:05

score 3 · Answer 2 · answered Apr 01 '17 at 10:31

An alternative solution to parse integers from strings:

#lang typed/racket

(: numerical-char->integer (-> Char
                               Integer))
(define (numerical-char->integer char)
  (let ([num (- (char->integer char) 48)]) ; 48 = (char->integer #\0)
    (if
     (or (< num 0) (> num 9))
     (raise 'non-numerical-char #t)
     num)))

(: string->integer (-> String
                       Integer))
(define (string->integer str)
  (let ([char-list (string->list str)])
    (if (null? char-list)
        (raise 'empty-string #t)
        (foldl
         (λ([x : Integer] [y : Integer])
           (+ (* y 10) x))
         0
         (map numerical-char->integer char-list)))))

Converting String to integer in Scheme

2 Answers2