Madlibs Iteration 10

madlibs_iteration_10.rkt

#lang at-exp racket

(require (for-syntax racket/match))

(define prompt-responses
  ; Hash's list must be of cons of key value pairs such as (cons adjective null)
  (make-hash (list )))

(define (ask prompt)
  (display prompt)
  (read-line))

(define (lookup-or-ask var prompt)
  ; Given a variable and a prompt, checks if we've already recorded a response and prompts if necessary. Returns
  ; stored or new response.
  (if (null? (hash-ref prompt-responses var null))
      (let ([response (ask prompt)])
                (hash-set! prompt-responses var response))
      null)
  (hash-ref prompt-responses var null))
   
(define-syntax (blank stx)
  (match (syntax->datum stx)
    [(list _ var prompt)
     (datum->syntax stx `(lookup-or-ask ,var ,prompt))]))

;; Story templates

(string-join (list "There once was a big " (blank "adjective" "Adjective: ") " tree in the old forest of "
 (blank "location" "Location: ") ". Yes that's right, in " (blank "location" "discarded")) "")