Question

the format can turn any type into a string, e.g

(define lam-form (list `lambda (list `x ) (list `when (list `> `x 0) (list `* 100 `x ))))
(format "~s" lam-form)

result will be: "(lambda (x) (when (> x 0) (* 100 x)))"

Then my question is: how to do the reverse? meaning, turn "(lambda (x) (when (> x 0) (* 100 x)))" back to '(lambda (x) (when (> x 0) (* 100 x)))

Answer 1

Use read.

Welcome to Racket v5.1.3.1.
-> (read (open-input-string "(lambda (x) (when (> x 0) (* 100 x)))"))
'(lambda (x) (when (> x 0) (* 100 x)))