I tried the following function to conver a String to an Integer.
#lang typed/racket
(: myconversion (-> String Integer))
(define (myconversion str)
(string->number str))
The error given is :
Type Checker: type mismatch
expected: Integer
given: (U Complex False) in: (string->number str)
I guess this is because a number is not an Integer.
How to proceed?
I found the following code on internet , but this looks like a real
overkill for this simple problem ,
(: 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)))))
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