18-8-20-- string-join

#lang racket

(define add3
  (λ (a)
    (λ (b)
      (λ (c)
        (+ a b c)))))

(((add3 1) 3) 5)

(define table1-λ1 (add3 1))
(define table2-λ2 (table1-λ1 3))
(define put-it-all-together-λ3 (table2-λ2 5))

put-it-all-together-λ3


(define add
  (λ (c b)
    (+ c b)))

(define sub
  (λ (c b)
    (- c b)))
    


(define integer
  (λ (c)
    (λ (cmd b)
      (if (eq? cmd "add")
          (+ b c )
          (if (eq? cmd "sub")
              (- b c )
              "no command found"
              )))))


(define integerrr
  (λ (a)
    (define addd
      (λ (b)
        (+ a b)))
    (define subb
      (λ (b)
        (- a b)))
    (λ (cmd arg)
      (if (eq? cmd "addd")
          (addd arg)
          (if (eq? cmd "subb")
                   (subb arg)
                   "not found")))))

(define string-join
  (lambda (ls delim)
  (define out (open-output-string))
    "Join list of strings together by delim into one string."
    (let loop ((ls ls))
      (if (null? (cdr ls))
          (begin
            (display (car ls) out)
            (get-output-string out))
          (begin
            (display (car ls) out)
            (display delim out)
            (loop (cdr ls)))))))


(define name
  (λ (a)
    (define firsty-lasty
      (λ (a b)
        (string-append a b)))
    (λ (cmd b)
      (if (eq? cmd "combine")
          (firsty-lasty a b)
          "don't combine"))))


(define names (name "john"))
(names "combine" "doe")








        
    











         
(define int2 (integer 2))
(int2 "add" 3)