#lang racket

;; CSE 413 16au
;; Lecture 7 sample code
;; Hal Perkins

(define nums '(1 2 3 4 5))
(define rnums '(17 3 -2 42 15 3 12))
(define alist '(a (b c) d e))

(define (incr n) (+ 1 n))
(define (dbl n)  (* 2 n))

;; review: curried functions

;; ordinary add function
(define add
  (lambda (x y) (+ x y)))

;; curried add - result is a function that has an
;; integer parameter and returns the sum of that
;; parameter plus the (frozen) value of x
(define cadd
  (lambda (x)
    (lambda (y) (+ x y))))

(define plus2 (cadd 2))


;; (add 2 3)
;; ((cadd 2) 3)
;; (define plus2 (cadd 2))
;; (plus2 3)

;; copy of list where lo <= x <= hi
(define (filter-in-range lo hi lst)
  (filter (lambda (n) (and (>= n lo) (<= n hi))) lst))

;; return function that will filter a list for values lo <= x <= hi
(define (cfilter-in-range lo hi)
  (lambda (lst) (filter (lambda (n) (and (>= n lo) (<= n hi))) lst)))

;; (filter-in-range 5 20 rnums)
;; ((cfilter-in-range 5 20) rnums)

(define filter520 (cfilter-in-range 5 20))

;; (filter520 rnums)