The worst racket string program

the-worst-string-program.rkt

#lang racket/base

(require racket/unsafe/ops)

(define s1 (string-append))
(define s2 (string-append))

(immutable? s1) ; false
(immutable? s2) ; false
(eq? s1 s2) ; true (!!!)

(unsafe-string->immutable-string! s1) ; changes s1 to immutable and returns s1
(immutable? s1) ; true
(immutable? s2) ; true (!!!)