racket basic

 #lang racket

; define a constant

(define myval 3.14)

; function without param

(define myfunc

  (λ ()

    (+ 3 4)))

; call function

(myfunc)

; function with param(which is one formal)

(define myfunc-mul-two

  (λ (x)

    (* 2 x)))

(myfunc-mul-two 4)

; outer function calls inner function

(define double-result-of-f

  (λ (f)

    (λ (z)

      (* 2 (f z)))))

(define add3

  (λ (x)

    (+ 3 x)))

((double-result-of-f add3) 4)